Your website describes you as racer, an engine builder, a TV presenter ... and a tea junkie. It’s 11.30am on a Friday. How many cups on the day so far?

How many have I had? [Thinks] Seven cups of tea. I’ll probably have 20 before the end of the day.

Your GP can’t be happy with that.

I’ve not had a problem with it. I sleep all right. I can sleep on a bloody washing line if I want to.

People know you best in your two outward-facing roles – as bike racer, or as TV presenter. But you spend the vast majority of your time as a mechanic, servicing trucks. Why?

It’s a good balancing act. With the trucks, I’m in at 5.30am. A gearbox in bits, the bloke might be coming to pick up his truck that afternoon ... I’ll think, ‘Bloody hell, I just want to go and race my motorbike.’ But then I go racing for a couple of days and I want to go back and fix my trucks. And when I’m sick of both of them ... I might want to go off and do a bit of filming for TV [he recently presented a second series of Speed with Guy Martin for Channel 4]. Not very often that day happens, that I want to film. But they all complement each other.

You don’t like the TV work as much as the other parts of your life?

Channel 4 keep coming up with ideas. If I went in to that work full time, they’d have something for me to do every day, filming-wise. But I’d become one of them – not brainless, because some of them are clever – but a TV presenter. Passionate about anything that they’re told to be passionate about. Such a fake industry. And that’s not me. I wouldn’t want to do that as a job.

How hi-tech is the day job, working on trucks? Can it be done with a pair of overalls and a set of spanners, or is it more complicated than that?

Not really mate! As long as you’ve got your toolbox ... No, you’ve got all sorts of stuff for trucks. Presses. Welders. Windy guns. Jacks of all shapes and sizes. Parts washers. Loads of different types of oil. Computers. It’s not rocket science, my job, but yeah, it’s not quite as easy as having a set of spanners. You need a lot of gear to fix trucks.

How do the computers factor?

You plug them in and use them to diagnose problems.

Plug them in to the truck?

On the dash. And then you can talk to all the separate ECUs [engine control units] on the truck. You can’t work without a computer now. Everything’s changing so fast. Updates all the time – our computer is updated four times a year. It isn’t as easy as just probing about with a torch anymore. You can’t shy away from technology, though, because it’s happening. It’s happening. You just have to go with it. Otherwise what are you going to do? End up working on 40-year-old trucks?

Your dad repaired trucks when you were growing up. Does it ever feel like cheating to use computers for someone who grew up in a more manual age of vehicle repair?

The computers don’t always tell you what the problem is. Sometimes they just point you in the right direction. It’s not cheating! It’s probably harder now than it was back then. Having said that, engines now – bloody hell – they’ll do like a million kilometres before you have to put a spanner on them. Back 15 or 10 years ago, we’d be rebuilding engines all the time, every month.

In what other ways has tech changed the truck business?

Last December something called Euro 6 came in – new European restrictions about the amount of nitrous oxide in the exhaust that leaves the engine. All trucks since then have had to meet those restrictions on emissions, by using something called SCR, selective catalytic reduction, in combination with EGR, exhaust gas recirculation ... I started in a truck yard when I was 12 years old, working weekends and school holidays. I remember my eyes would be running with the diesel fumes. Now, the gas coming out the exhaust is nearly as clean as what’s going in. They’re bloody clean now. So many electronics on board.

Is that where we’re heading: a world of electric HGVs?

I can’t see why it’s not happening now. There’s so much energy recovery to be gained from a truck. So much scope for regeneration because of its weight. You’ve got 44 tonnes’ worth of truck going down a hill and you’ve got to reduce that speed, turn that kinetic energy into another form of energy – heat, the only way to get rid of it, using hydraulic retarders on the gearbox which slow you down, and friction brakes on the wheels which slow you down. That’s wasted energy. You’re wasting so much energy to stop a truck when you could turn that energy into electrical energy, store it in batteries, then use it to boost you up a hill.

Like KERS in Formula One.

Yeah. I’m sure truck manufacturers are doing something with [that idea], but I’ve seen no sign of it yet. But that’s the way it will go.

I expected you, as a self-proclaimed “pistonhead”, to be more sceptical about electric vehicles.

You can’t shy away from what’s happening. And it’s happening. But full electric [vehicles]? I’m not all for that, really. Not until nuclear fusion’s sorted [as a common, consumer source of power]. Otherwise, electrical energy, it’s bullshit, really, for all these green freaks, isn’t it? You know, with hybrids, with electric cars, all you’re doing is burning fossil fuels in a power station, sending it down a power line, and putting it into your car. And what we’re doing is burning fossil fuels in an internal combustion engine. It’s the same end result, you’re just burning a fossil fuel in a different place. When nuclear fusion’s sorted – another 50 years I reckon – that’s when we can make electricity more efficient. Until that day? I think it’s a load of shit.

Another hypothetical. Electric trucks ... without drivers?

Yep. Coming. In 20 years there’ll be driverless trucks. Put all the truck drivers out of work. But all the trucks will still want looking after, so I’ll be all right. I’m sure it will make for safer driving. When I was starting out as an apprentice, that’s when the electric throttle was coming in. And all the old boys were: “Ooooh, bloody hell, how unsafe’s that, if the electrics fail, it’ll be a disaster ...” Well: electric throttles [have proved] far more reliable than a mechanical setup. They’ve never caused any grief. There is no problem. You can’t shy away from change.

What about mechanics’ apprentices now. Is it a harder skill to learn, in a tech-dominant age?

Kids now are all bloody Facebook. Internet. They should find it easier. There’s more incentive for them to come in to the automotive industry, maybe. But there’s no interest. We’ve had three apprentices [in Martin’s garage] in the last two years. Good lads. Nice lads. Lovely lads. And bloody useless. We’ve sacked them all. Whenever you turned your back they were on their phones. All they wanted to do was get home, get on the internet. No interest. No spark. Me, I’m still passionate about the job. I can’t get in quick enough in the morning.

Why keep on the day job at the garage? Why not take your TV earnings and live an easier life?

I dunno. I dunno. I dunno. I love it. I always like the dog to wag the tail. All right, you earn decent money on TV. But I earn decent money on me trucks. The day the TV boys get sick of me, and that day will come – course it will, you’re kidding yourself if you think otherwise – what would I do then? If I was a TV presenter, I would have got in to the luxury trap. Earning mega-money. And the next thing you know they’ve sacked you. The money stops. And you’ve got a massive mortgage. And you think: “Shit. Shit.” And you have a massive breakdown. And you have to go to the Priory.

I’ve never got above my station. Nice house. Nice shed. I drive a Transit van and a Volvo Estate. I’ve never lived like a rock star. No mansion. No cocaine habit to fuel. And if everything stopped tomorrow I could quite happily live on my truck wage.

Are those really the only vehicles you own, a Volvo Estate and a Ford Transit?

My Volvo Estate’s nice, it’s real nice, a 1968 [model], a right rare thing. Dear. And I love my Transit van. It’s mega. Auto-dipping headlights on that. I’ve also got a couple of motorbikes. Three motorbikes. A dirt bike; a bike I’ve built to go and do a race in America this year; and then an Italian bike.

What’s your insurance premium like? It wouldn’t take much Googling to find out you like going fast.

No lies are told. I’m a truck mechanic from Grimsby. What’s the problem? Motorbike racing is just a hobby, like the TV work. It’s not a job. You don’t have to declare that on your insurance, do you? A hobby? Ask me no questions I’ll tell you no lies.

Do you belong to a breakdown service?

Ford Transits don’t break down, mate. [Laughs] I’ve never been given anything off Ford. I should be paid to be a spokesman for Ford Transit. But it’s true. Transits don’t break down. You don’t need a breakdown service.

You’ve been mountain bike racing a lot recently haven’t you?

I probably do that more than motorbike racing now.

Because it’s safer? You had that horrendous crash on the Isle of Man that was a feature of the documentary, TT, star of 3D: Closer to the Edge.

No, no, not at all. That film we did and the TV ... it’s sort of made racing a bit of a pain in the arse now. Go racing and I can’t have five minutes to myself. I’m not an ungrateful person. The support I get is great. But I can’t have five minutes’ peace. A way around that was to go and race a mountain bike. Sometimes I do 24-hour races. I still love motorbike racing – I love it because it can kill you; that’s why I do it. But the mountain bike racing I do for the mental side.

How can you love something because it can kill you?

Well, everything in the world has been bloody sanitised with health and safety, hasn’t it. There isn’t really anything left in the world where you can go out and actually kill yourself. I like being in control of my own destiny, really. You can go out racing on your bike, make one little mistake, and that’s it: you’re dead. I love all that. Being so near yet so far.