Speed Week: TG cuts the grass

In a Top Gear world littered with stupid stunts, driving a 130mph mower ranks up there as being one of the more unhinged. Trundling out of the pit lane for a lap or two, it dawns on me that although a lot has been added to this Honda mower - a 109bhp Honda VTR FireStorm motorbike engine, for starters - it's also missing a bit. There's no seatbelt (the idea being you're thrown clear in an accident), no traction control (the idea being... actually, I don't know why I won't need that), no airbag, no ABS, no roll cage. But it does have a petite fire extinguisher strapped to the rear wing. Oh good.

But before we get into the terrifying prospect of driving it, a bit of background: how on earth did we end up here? This should have been some ultra-secret development project years in the making, but in reality this small projectile of landscaping lethality was born from a throwaway conversation with Honda about three months ago. Summer was on the way, Top Gear needed the grass cutting, and we thought the mower world needed spicing up. So Honda and Team Dynamics (the company that runs Honda's touring-car programme) went away and had a think. Turns out the skunkworks department decided "spicing up" meant "completely deconstructing and blowing apart" the ride-on market.

What they have produced is based, in the loosest sense of the word, on the HF 2620 Honda lawnmower. But very little, bar the body panels, clutch and brake pedals, remains from the donor.

Top Gear's very own Blade Runner has a spaceframe chassis, like a proper racing car. Part of the grass collector - that skirt-like thing at the back - is filled with a sectioned-off area that contains the fuel tank and various radiators. Under the bonnet is a Honda VTR bike engine, producing 109bhp and 71lb ft. Plenty, when you consider that the entire thing, complete with terrified driver, weighs just 205kg, meaning the power-to-weight ratio is 532bhp/tonne. For a knuckle-whitening on-paper statistic, a Caterham R500 has a mere 520bhp/tonne...

Top speed is roughly 130mph (no one's done more than 30mph before today), and the 0-62mph time is probably around four seconds. Though, needless to say, that speed isn't possible when you're mowing because with the cutting deck attached, the ground clearance is about a centimetre. But cutting grass is indeed still possible - Honda has fitted two 4,000rpm electric motors with metal brake cables attached to flail the green stuff into submission.

The tyres are nicked from a racing quad and are as soft as marshmallows. Apparently, if they were any harder, there'd be so little grip that the mower would swap ends as soon as you got on the throttle. The Team Dynamics boys tell me this just as I'm driving down the pit lane. Thanks, chaps.

As I head towards the start line, all I'm worried about is not falling out. How can something with a wheelbase comparable to a toy car possibly be stable? The noise is ridiculous - like the bastard offspring of a nuclear explosion and a machine gun - and it's spitting small blue and orange flames from the side-mounted exhaust. My leathers suddenly feel inadequate.

Still, no time to worry about that now. The Stig is stalking towards me, so I need to get my drive in sharpish before The Figure in White steals the Honda for the rest of the afternoon. There is grass to cut.

Build the revs, drop the clutch, wince, pray... and it fires up the pit straight with such ferocity that I'm pretty certain I left some of my internal organs behind.

There is absolutely no slack. Instant power, instant gear changes. The ratios are so short and it revs so freely that I'm in fourth within fifty yards. There are two gearchange buttons on the steering wheel - one for up, one for down - and I'm through the first corner in a blur.

There's a straight just after, which gives me a chance to stretch the Frankenmower a bit more. Lean on the accelerator, wince again - well, you try riding a flame-spitting garden implement at 80mph without being slightly circumspect - and we roar into the distance and around the Circuit de Charade. It feels... incredible. An experimental vehicle at full bore. This must be a bit like how Andy Green felt before he went through the sound barrier in Thrust SSC for the first time. Sort of.

But it's a tribute to Honda and Team Dynamics that the mower doesn't bite back. Granted, I'm not really leaning on the brakes - I can't heel and toe with motorbike boots on - but, despite all the noise, it's actually fairly easy to drive. You're locked into the tiny seat so tightly that your arse can feel every single bump. The steering isn't as brutally sharp as I thought it might be, given how short the wheelbase is. Towards the end of the lap, my confidence gets the better of me, and I decide to see what's really possible. We hit 100mph, and I must admit to a fleeting thought at this point - if this goes wrong, quite a lot of pain isn't far away.

But the mower and I survive, and as I round the final corner, the red Honda popping and banging like an angry firework, The Stig is waiting at the start/finish line. It seems he cannot wait any longer. Presumably because this means he can legitimately cut corners and shave seconds off his lap times...