Police have cordoned off the surrounding crowds and we've got our own motorbike escort. I feel like a royal, which is handy considering the heritage of the car I'm in. It's a 1953 State One Royal Review, used as part of the Queen's Commonwealth celebrations. It's travelled all over the world and, I'm told by co-driver and engineer Martin, missed only a few beats in its time.
It certainly feels different to the modern, air-condititioned diesel I've driven down here in this morning. I've not driven a classic like this before, and I notice very quickly just how much hard work is involved.
Let's start with the steering - of course, it's not power assisted, and there's a fair amount of effort required to get the beast to turn. There's some grunting on my part and, as I lift the clutch for the first time, some groaning from under the bonnet, too. I'm told that's normal.
We make progress down The Mall, as early tourists snap pictures of this most peculiar sight. It's part of a heritage drive organised by Jaguar Land Rover to showcase its royal connections, and there are certainly a few of them down on The Mall this morning. There's a 1967 88" military specification Land Rover, producing in the region of 72bhp from its 2.25-litre engine - it was built in Germany and used primarily by royals for inspecting the troops.
There's also a 1955 Mark VII M Jaguar saloon, famously owned by both the Queen and the Queen Mother between 1955-1973. A top speed of 101mph was acheived from its 160bhp, 3.4-litre engine. I'm told we'll be getting nowhere near that speed this morning.
There's also a pair of Royal Range Rovers, kitted out to carry royalty in the back while keeping entourage and driver comfortable in the front. It's quite amazing to see these vehicles in the same place, given their lifetime of shared royal history.
Back to the State One, however, and there's a problem. I've gone to try and put it into first only to find reverse, and the gearbox has jammed. With a slow shudder we grind to a halt, and I'm told that although this has happened before and it's a relatively easy fix, we won't be moving anywhere for the moment. Still, there are worse places to break down, even if the Houses of Parliament aren't giving us much privacy.
It's a quick push to the side of the road and a call to the backup crew to bring the spanners. Martin explains that the gates that hold the gearlever in place have jammed, effectively locking the transmission. Eventually backup arrives, and with the help of a trusty tool set we're back on the road, waving goodbye to the decent-sized crowd we've gathered during our stop. People love to stop and stare at the Land Rover, and some ask about its royal connection. I can believe this car has travelled all over the world, the steadily fading interior can speak of that, but I'm surprised at how involved driving it feels.
As with any classic car, there are things to be learnt and tips to be picked up. I learn not to downshift into second until we're stationairy, and after a few miles I learn that, given enough space, braking force can be applied without descending into panic.
At the end of it all we pull back onto The Mall, and reunite State One with its royal bretren. I'm pleased cars like this are being cared for and still used - albeit rarely - though, if I'm honest, I'm very glad not to be driving home in one.