The car, with her many modifications, is on test, and in honour of a guest for the day is temporarily re-named for the day. Well, she was going to be, until the guest never showed and left poor Helen wearing someone else's name, which is simply wrong.

On the scales the car comes in at 1585kg with just under 10 litres of fuel, so she’s spot on the weight, if she’s running she’s legal. It’s so close though that I have to now keep track of my own weight, a hard week in the garage and suddenly the car’s 2kg illegal…

Main aim of the day is the T1R v R1R test, and to do that we need to shake the "new" car down, and set a benchmark time for the T1R tyre in this new trim. 70kg extra weight, remember, and there are a lot of hills and bends to accelerate that round, we are expecting it to punish us quite badly.

Last time the car ran here at that weight was in ’08, it was about 1570 or so, and stuck behind Stewert we never cracked the 1.51 laptime. Helen set a 1.48.5 here at the trackday last year, and the benchmark race time is John Lock’s 1.48.8.

Basically we need to know how close to a 1.48.8 we can get a T1R car at the new weight limit, with the standard 3.54 diff.

Answer? Very. Chief Engineer’s sneaky stopwatch clocks a 1.48.9, and despite his comments that I don’t appear to be trying very hard yet, we’re calling that good enough, confirmation that the car is in the ballpark.

It’s true that there is more speed to find, it’s a trackday so I’m not 100% all out, and I’m playing with the old Mintex pads I used to run, so the car is a little bit unknown. More tail happy on the brakes, which is fine, means they’re finally working. Despite caning the brakes all day long, pad wear was minimal, and we never even threatened to warp the brake discs.

I have no option but to say that with that in mind, the Mintex is a better pad for me than the Ferodo. Nothing like that same bite, the Ferodo wins all day long in terms of sheer "I think I just drove into a wall" stopping power, but they were murdering my discs every other race no matter how long I took to bed them in, and that’s at least £50 extra in brakes per weekend. In fact on the basis of this data it appears that it is half the cost to run Mintex than Ferodo.

My only other option would have been to upgrade the rear brakes to X300/XJ8, the bigger pad may have allowed me to play with Ferodo all round without the braking imbalance.

So yes, that laptime is with inferior but more user-friendly brakes.

I have my poor old dad strapped in the passenger seat, and once again I think his eyebrows went up a few notches at experiencing the reality of the XJS at pace. His only prior time in the seat with me was Brands trackday in ’08, and I’m at least 5mph faster these days. Bedding brakes in initially gave a relaxed lesson in Cadwell’s geography, for those who have only spectated from the café, there’s 75% of the track unknown, and to find that vast back section you can’t see tends to stun people who think they’ve been here.

We even let him have a play later on. Didn’t dare watch, because I knew he intended to press on a bit to find whether he still has it, but it kept coming back round intact.

The new exhaust makes some lovely noises, ask the MX5 driver who claimed his brain vibrated in his helmet as I came past, and I think the car has a hint more go, it’s so hard to tell here. The only way I can monitor speed is by reference to rpm. Pick a spot on the Armco as you come onto Park straight, check every lap what rpm the car is pulling to see how well you got out of turn 3, gives you an idea whether you’re going any faster. It suggests that the car is pulling as well as she did without the extra ballast.

It’s not enough, I would really like some actual power instead of tiny tweaks to standard engine, but the ported head I dream of is still just a fantasy. In fact I rather suspect my beloved team are not going to let me have any more power at all, there is a conspiracy afoot to keep me to a certain performance level this year. That said, given the tyres, probably a good thing.

That blue thing on the bootlid? Told you I was redesigning the spoiler.

Handling is transformed over 2009, I can trust the rear end again. There is a hint of corner-entry oversteer, and what feels like more rear roll, but with an extra 70kg in or around the back seat area that is to be expected, I think that’s physics rather than ill-handling traits. And the fact that the rear wheels are getting so hot from the brakes now is causing the tyres to go over-temperature. Of course then oversteer begets more pressure and more oversteer, I can see now why some D class cars struggle not to drop the rear end.

It is, however, perfectly manageable, it’s not vicious at all, at least here. I said that last season and look what happened at Coram!

With trackday traffic, rules and regulations we never set a full-on blistering lap, so when we started floating about in the 1.49s, and dipped to that 1.48.9, we called that a day for the T1R. The swap to R1R revealed 2 things, both of which chief engineer assaulted me for.

1. The n/s/f wheel had only 2 nuts done up.

2. The tyres were rather, erm, old, and kinda bald. Oops.

We had set the pressures, but with a borrowed gauge, and as it turns out, Roger, your gauge is woefully inaccurate.

Let me put it this way, if you set out on a tyre at a given pressure, get it hot, bleed out 6psi, and let it cool, you would expect to lose some cold pressure, right? Measured with my own, rather better gauge, that cold pressure was only 1psi lower. I am going to locate the Beard’s pressure gauge and distance test it for him, it’s lying. How many poor sods are setting tyre pressures with complete junk by way of pressure gauges and not getting a true reading?

The only thing we can say is the same gauge was used to set R1R pressures, so at least the test was consistently wrong, they may have all been running 3 or 4 psi higher than they should, but they were all doing it.

So to the R1R, and it was a complete mystery to me. I’ve never run race rubber, only ever has the T1R been fitted to this car, I’ve no idea what’s coming.

Into the hairpin first time out, and I can’t resist trying it, go in a bit hot, turn the wheel, and find myself exiting the corner without fuss or drama, it just went round. Right then!

4 laps of grief to get them hot, then into the paddock to let them cool. Being impatient it strikes me that driving them across the wet grass is a quick way to achieve the goal, and within a minute we’re heading back out for another 4. There are road cars out here on full 888-type tyres, one yellow hatchback thing insists on getting in my way for over a lap, and I’m not allowed to dive on him, the ignorant sod blocks me because he thinks it’s a race!

Eventually we pulled the classic D class pass on him, hang back on the way into the corner to get a gap, then sling it in and get on the throttle early to slingshot past with high exit speed, no sense sitting off the bootlid when you don’t have a lot of power. It’s that need to engineer an overtake that makes D cars such a challenge to enjoy, and the reason spectators think some of the cars have much more horsepower than we really do.

In and let them cool. Heat cycling complete.

Proper laps then, a hot dozen to work the rubber, find the grip, and in to set pressures. The rear has started to slide, even on the massive grip these things afford. Pressure check tells why, they put on 12psi, 6 more than the fronts.

Possibly the brakes again, because they are now taking enormous abuse. The tyre is now better than the brake, the stopping capability of the car is finally down to the size and type of the pad, calliper and disc, which was never the case before. The car with Mintex pads all round is a little tail-biased on the brakes, but it helps overall as you don’t simply smoke a front tyre, there is more feel to pedal.

Ferodo pads give greater bite by far, but the grip now is such that I think we would test even Ferodo capability, I think the front discs would die very quickly, and frankly flat-spotting tyres that cost this much is not an idea I like anyway!

We have, however, easily found the limit of the brakes now, whereas no combination of pad and tyres has ever before got me to the point that you can lump on the brakes hard and just keep your foot in. There is a drawback though, in that I think we’re getting the pad floating a bit on its own gas buildup. Despite drilled discs there is an issue under lower-speed braking at the hairpin. Having hit the pedal at the Mountain and Hall Bends, I fear the pad is warm enough by the hairpin that it quickly cooks, because it isn’t interested in taking off that last couple of mph, the car just drives on.

I do have to remember that we’re carting 70 extra kilos about, but the feeling is unmistakable. It is possible we could see some daft low-speed class D rear-end shunts. Glad I got a rear bumper fitted.

With pressures set we do some proper laps. It’s mostly about belief that the car will do it. Turn 1 becomes a hint of brake, then a lift, and finally flat. I won’t disguise that it took me some really deep breaths and some talking to myself on the way in to convince myself that at 110mph I really can just turn into an uphill left hander in 1.6 tonnes of rubber-suspensioned barge and keep my foot planted, but she does it.

In fact she does it quite easily, and it’s depressing to hear the engine note change as the hill actually takes speed off me despite full throttle. It is really steep there, but can you imagine explaining to another racer that there’s a corner that you go through flat out and still lose speed due to gravity?

The car can be reefed over to the left to make turn 2, and here, despite the rubber, there is understeer, sheer mass pulling the car wide, I can feel the tyre scrubbing, it must cost £5 to take this corner.

Turn 3 is of course critical, and the classic late turn still works as well as ever, the grip allows the throttle to be planted very early. Eyes right to check that spot on the Armco for an rpm reading!

Back end of Park and into Chris are, for me, where it again shows the difference. On the T1R was 3rd or 4th gear last season for the right hander, it’s all in the rpm on the exit as to what I should have done with the stick. Today the extra mass has made this a 3rd gear corner, on the throttle as early as I dare, flirt with the grass, grab 4th, feather on entry to Chris, and power all the way through with the odd chicken feathering of the throttle.

The R1R is turn the wheel in 3rd, nail the throttle almost before you’ve turned in, drive out easily, grab 4th and full power from the moment you have the gear to the moment you hit the brakes for the gooseneck.

The gooseneck can also be attacked harder, you can hit kerb on the left and not be thrown wide onto the grass now.

Oddly the Mountain and Hall bends section doesn’t really change in terms of approach, I think the T1R is as fast there as the R1R, but it’s such low speed stuff it’s harder to tell. We do manage to collect a couple of bollards though, so the year has begun at last.

Best time we managed was a 1.47.6, but that’s not the ultimate class D time, that was the only clear lap, and not at full attack. Later there were faster sections, but none all strung together into one clean full-tilt lap. I think that were you to combine the fastest charge at each turn into one lap the car is capable of 1.46s.

Make no mistake, this is a serious tyre, it clearly has much, much more grip than the T1R. I’ve long sneered at the 888 and similar tyres as being the coward’s way of racing, and this test did nothing to challenge that view, it is far easier to make this tyre get you round here quickly than it is the T1R, I could have lifted off by a good 5mph all the way round and cruised in easily ahead of the T1R-shod class D pack, that’s how good this rubber is.

Personally I like the drama of the T1R, the scream of tortured rubber, the car sliding predictably, the need to balance the car on the very edge and pick your line with care to keep hold of all that precious speed. It was almost disappointing to have the front turn so well and to be able to mash that pedal so early.

Suddenly the inadequacies in the class D car are apparent. There just isn’t enough power or stopping capacity to make use of this tyre. If I can lump on the power without much by way of concern because the car is too heavy and gutless to get me into any real trouble then where’s all the skill gone?

I know, I know, aspiring to 1.46s in a class D car and claiming boredom is a baffling thing to say, but really, other than turn 1 this track suddenly got a lot more dull, the grip has taken some of the awe away.

I have a great fear that this season is going to bore the tits off me.

Which brings me to one further point. I’m assessing the T1R as 2 seconds per lap slower than the R1R, which is about 1.5mph. At shorter, less twisty tracks, that will probably be less.

When we raced here last year I was 6 seconds per lap faster than the next D car even with the poor laptime I was pulling then. I’ve just taken another 2 off that time with the T1R now I can trust the car again, and think the R1R will go another 2.

But, there is a catch to all this. Tyre wear. This test did massive damage to those R1Rs.I assess the left front as half worn after a single afternoon of maybe 30 hot-ish laps.

There is no way they are going to last a season if I use them to their limit, in fact I’d be amazed if they make it through Snetterton. Think about it, I’ll bet that from the Esses to Russell is going to be flat out. There is the grip to do it, but the weight of this car doing it is going to rip that tyre apart.

What this rubber does then is offer a horrific tease. The ability to go much faster, if you can afford the bill. I can’t. The modified boys with ¼ ton less weight and wider rubber are not going to suffer the same. Helen’s sheer rubber to tarmac psi is so high that she really does grip, but at the cost of huge tyre wear. A class D car has roughly 20% more pressure per square inch of tyre on tarmac than a class E, I believe that’s why they get hold of the floor so well with the T1R and why they like the wet. I think she would still hang with the class E cars, but that it will cost a huge amount of money to do so.

In short, I can now only go as fast as I can afford. It may be then that the days of really annoying the modified cars is over, not on merit, but on wallet. That’s rather upsetting.

Run T1Rs for the year and race at a disadvantage? It would make class D much more competitive. Run R1Rs and go just fast enough? Where’s the fun in that? This trackday test has rather depressed me. The tyre’s fast, but it’s a bit boring, and I think it’s about to ruin my entire year.