but how fast is it?

Some people say it's as fast as a GT3 car.

We just happen to have a GT3 car.

Bill, where's my race suit?

Now this really was just a day out and not a scientific exercise,

and it was recorded last summer in August 2018,

so apologies for the basic footage.

I wanted to drive them back to back

to see just how different the supposedly best track machine was

compared to a proper racing car.

The Senna is spec-sheet pornography:

800 horsepower, 1,300 kilograms active aerodynamics,

750,000 pounds and a carbon tub,

sub-10-second standing quarter-mile and lap times to make a P1 look slow.

The race car has just 550 horsepower,

weighs a bit less than the Senna

but has the benefit of wider slick tyres and conventional care aerodynamics,

and it looks miles better covered in crap from the Spa 24 hours.

I love the way you could see out through these windows down here.

I thought they were an absolute gimmick when I saw the car being revealed,

but actually, they add to this sense of airiness.

There's glass everywhere,

so you have this lovely sense of light in the cabin,

which i think is great,

so that McLaren Senna... what a name, hey, Senna.

It's probably the coolest name you can apply

to a car that you could use on the street.

You have to be pretty sure that you're making something

that's worthy of that name.

800 horsepower under 1,200 kilograms, so I'm told,

so it's light.

The numbers are staggering.

I'm told it's P1 quick. I can believe it,

and yet it's road-legal. It has road-legal tyres.

It has number plates. It has indicators.

You could drive it to the South of France and back.

What do you think about the way it looks? I think it looks like a dog's dinner,

but then you probably didn't see the shorts I was wearing earlier.

I've got no idea about aesthetics.

It could have been a bit more beautiful,

but I'm told it's all about function, aerodynamics.

Well, we're at Silverstone, so let's see what those aerodynamics are all about.

First impressions: the engine mighty. Absolutely mighty.

The system's very, very helpful, pulling big numbers down the straight.

Jeepers Creepers, brakes superb for a road car.

Again, that's the best I've felt in a road car.

Superb pedal feel, massive reassurance, but already, it's--

I get this sense that it's held back by the tyre,

that little 245 front tyre. I got understeer.

Throttle out, again, just the front of the car is washing out.

Means I have to wait to get on the throttle.

I mean compared to any other road car I've driven on a track,

it's different gravy. I'll give you that. It's just better, faster,

but I don't know the expectation is so high, isn't it,

you're thinking, 'Come on'.

So we're in race mode. I'm not turning everything off,

because this car belongs to a mate of mine.

I don't fancy the tyre bill, and also it has to be representative.

This is the way people will drive these things.

We're doing a track day

because I'm not spending all that money, renting a circuit and all that rubbish.

This is just about getting in them, doing a couple of laps

and just confirming either way which is quicker.

The air that I may grip for the quick stuff is mega.

I mean it's unlike any road car I've driven before.

You can really lean on the car at high speed.

Interestingly, it prefers to be using the torque of the engine.

It seems to respond better the more you use rpm.

It seems to lift the front of the car a bit,

which I haven't expected. Systems are working hard.

I mean it's not a difficult car to drive, but it is...

You're busy making little alterations and corrections,

just needling it around a bit.

Braking is absolutely superb,

and the braking stability, the way that you can use steering angle

and stop at the same time is, again, not like any road car I've driven.

Let's see what it's like out here.

Traction's good a little bit of a spoon up there

into fourth gear through wood.

I'm staying flat. It wants to run all the way out.

What's it doing now? One five something. That's beyond the race car at Blancpain.

Now, yeah, I've got some understeer there.

It was just a little bit understeery on the way out there,

and the high-speed stuff here, yeah, look at that,

just staying pinned in fifth, 125 miles an hour.

There aren't many road cars that can do that.

Yeah, so in many ways, I think it's a triumph,

but then there is this claim,

there is this it's as quick as a GT3 car thing.

I'm not sure it is.

It's a fast car, but I'm surprised at how limited it is by its front axle grip.

I didn't expect so much understeer, I really didn't.

I thought it would be better than that in that respect, so, I don't know...

Maybe it just needs a different tyre or something, but...

Thirty-two four five at the front, so it's lacking some size in that area.

Yes, it's mighty. It's absolutely mighty.

But I just expected a bit more from the front axle.

That sounds like the meanest thing anyone's ever said, but...

the rest of the cars so impressive.

That's the one aspect that does...

It's highlighted by the car's brilliance in other areas, really.

Enjoy the Balaclava look.

So I can have a quick go in this car.

This isn't the race car I drive. This is a sister car,

because our car doesn't look so pretty after Spa,

so go out, make sure the seat fits,

pop some tyres on it and then we'll go and do a lap time.

It's simple. There are no data or nothing. Lap time.

I want to know whether McLaren's claim of the Senna being as far as the GT3 car

is true or not.

Senna then.

If you want to find out whether the Senna is quicker than a GT3 car,

you need to drive a GT3 car.

It just so happens that I've been racing one this year.

This is the 650s GT3.

Carbon top. It's the McLaren's staple but in racing form.

So it's the Senna really a racing car with number plates?

Well, from the off, it just isn't.

There's a directness to this vehicle. There's no rubber in the suspension.

The steering. Everything about the car is more direct than the Senna.

It's flatter. It's more planted. Its brakes are much stronger.

I mean the Senna's brakes for a road car are superb,

but these are, they're different gravy.

It doesn't have the ultimate power of the Senna,

but it comes out of corners so much quicker,

and immediately through comps, I'm going 15 miles and hour faster.

I got no understeer, relatively compared to the Senna.

So, yeah, immediately, it's the front axle on both that are so different.

I can lean on this because of the slick tyre

and just the width of the tyre in a way that I just can't in the street car.

I love racing this thing. It is such a fun car to drive.

Yeah, it doesn't have the grunt of the Senna,

but I can brake later everywhere,

because I just got more purchase on the track.

I've got a wider front tyre, and it's slick.

Systems aren't as intrusive either.

Whoa.

Let's try this with the quick stuff.

So fifth gear on entry, come down to fourth, throw it over the curb

and already now on flat top, that's full power.

Through the left, it's absolutely flat.

A little grip on the steering there as it moved a bit,

but really, yeah, it doesn't have the crazy moving rear wing,

but it generates a lot more downforce.

The GT3 car really is quite a machine.

It's so efficient through the air and through fast corners.

Good old-fashioned pneumatically actuated.

A manual vehicle. It's effectively really fast.

So I suppose it really remains to be seen which one really is quicker.

I mean, I know what my money's on,

but is there only one way to find out?

Yup. It's all about that front axle for me.

Yes, I've got more traction because of the slick,

but the front of the car is just there..

in a way that it isn't in the center. I like this car. I really do.

So, a pretty unspecial time by me.

But it was one lap challenge and I'm old and I'm chubby.

Next up, the Senna, which won't do many laps at a time

because it's fuel tank is so small.

So the Senna is miles slower than a GT3 car,

nearly seven seconds adrift round Silverstone,

and after the race car, it just feels flappy and unconnected.

And if that seems like an unfair comparison,

well, it probably is.

The Senna has aircon, and it will do the shopping,

but it's not remotely pleasant on the road,

so most people will just track them.

For the price of a Senna, you could buy a GT3 car

and do ten track days a year.

Now I'll tell you what. I know what I'd rather drive.