My stomach is churning, and the extended wait is giving it plenty of opportunities to do those mushy backflips that signify I'm out of my comfort zone. Yes, I'm sat in one of only four Vaxhall Astra 4S Group S prototypes and I'm in the most amazing traffic jams ever. Directly in front is a Lancia Delta S4; behind, an Audi quattro S1, and I'm familiarizing myself with Group B spec cockpit and controls, while trying to maintain a semblance of calm. Welcome to the Festival.

I love the Festival of Speed. I've been going as a punter for years, and given that the event offers enthusiasts the opportunty to smell, hear and touch racing cars that they'd normally only see on the TV or in books, it's utterly unique. If you're into pre-war, Le Mans, rallying, F1 or road-going supercars, there's an absolute welter of cars to appeal. But more than that, you can also bump into the drivers that made them great in the genteel (normally) setting, placed in the heart of the South Downs.

And I know I'm in an extremely fortunate position – I've been invited (last minute) to drive for Vauxhall up the hill; to join the innner sanctum, to - briefly - become one of those Goodwood heroes that I used to come down and watch. Well, okay, so they don't come to watch lucky writers; but they do clamour to see the cars, and that's good enough for me.

First I need to accliamatise with the car. And given I've never even seen it before, let alone sat in it, that's going to be amusing. The 4S certainly looks good, and far less extreme than most other Group B cars, such as the Metro 6R4 and RS200. But don't let that styling fool you. Under the clamshell bonnet is a breathed on Manta 400 engine, packing 350bhp, and allied with an XTrack 4x4 system. It's the real deal. And when strapped in and fired up, it's noisy vibratory, and thrilling.

I drive it from the rallying paddock and to the holding area to the top of the hill, joining the other Group B cars, and wait to drive the track. And wait. And wait.

But, boy, was it worth it - even driving down the hill to the start line was amazing. Thousands of fans lining the track, cheering and waving, make this a trly unforgettable experience, even if I'm still quickly learning the car. The gearbox is amazing - bang-bang-bang through the ratios - and the performance is intoxicating delivered through a light throttle. Down the bottom, we turn round and wait to go up. Sadly, after all that, we can't drive up - a technicality - and I end up following the safety car back up the hill, popping, spitting and roaring as we go.

But do you know what - I'm smiling. It's an unforgettable experience, and one I know I'm incredibly lucky to be experiencing. Thanks to the guys at Vauxhall for making it happen. Maybe next year!