If you follow janisj's suggestion, there's some free, on the street, parking behind the Royal Horseguards from Saturday afternoons to Sunday. But there are security issues (meaning the police don't like cars parked outside major government sites, not that cars get stolen) limiting the numbers severely.

There's quite a lot of free parking space along Northumberland Ave, though this fills up quickly on Saturday evenings. Waterloo Place and Carlton House Terrace, on the other side of Traf Sq, have more space, and I've never failed to find somewhere. Or ever had a car molested, however late on a Saturday night I get back to it.

Much obliged. A conflict does require staying in London the previous night. In a case of cost versus convenience/peace of mind, what would be the estimated fare and drive-time of a taxi from the Royal HorseGuards to Heathrow in the wee hours of a Sunday morning?

If one were to rent a car on Saturday and park overnight, would anyone know the closest car hire to the Royal HorseGuards (a possible neighboring hotel, perhaps) or a website which would determine such?

Thanks in advance…

Traffic in the very small hours can be surprisingly slow: Ken Livingston's real contribution to human misery hasn't really been the congestion tax, but the rephasing of London's traffic lights to force everyone to wait ludicrously long times at junctions.

So you need to allow 45 mins even at 0430, plus a bit in case the driver is unfamilar with Heathrow car hire locations. I think the current prebooked rate with justairports or Ray Skinner is about £25. Don't even dream of getting a black cab off the street.

The closest car hire place to you is probably the Avis at Waterloo station. BUT, Waterloo might stop being a serious place for hiring a car next week, when Eurostar services move north so the location might not still be profitable by the middle of next year.