Why does the richest man in government, a tycoon who could house, feed and clothe the cabinet if he saw fit (and decorum would allow) live in a hotel? Admittedly, it is not any old hotel. His is not a pad but a penthouse. An eighth-floor, fully serviced, luxury suite leased from the Grosvenor House hotel, on Park Lane, which overlooks Hyde Park. True, it's self-catering, but a BLT sandwich is just a phone call and a few floors away.
An apartment with a kitchen at these vertiginous social heights goes for £505 a night. 'If you stay for a month we could probably do you a deal but a week would be too short,' says a receptionist.
It was from here, with a little help from room service, that Robinson regularly entertained Gordon Brown, Ed Balls and the hapless Charlie Whelan, planning meetings, plotting manoeuvres and watching football on TV.
The convenience of the arrangement is obvious. But not as obvious as a cute little mews house in the city, which he could snap up for what must feel like pocket money.
But the long tradition of the wealthy staying in hotels suggests there are advantages to checking in to a plush apartment, too. Staff are paid to indulge your eccentricities, your capital is not tied up in bricks and mortar, and after a hard day's work you know the dishes will not be waiting for you.
Some have turned hotel life into an artform. Coco Chanel, the grande dame of perfume, had fresh camellias delivered to her room daily at the Paris Ritz during the thirties. Howard Hughes, the actor, had a suite at the Chateau Marmont in Los Angeles and used to have it scoured and disinfected every day. Writer Dylan Thomas spent his last few days marinating in bourbon at the Chelsea Hotel, New York; a couple of decades later punk icon Sid Vicious stabbed his girlfriend Nancy Spungen in Room 100 at the same hotel.
Salvador Dali used to take his pet lobster for walks down Park Avenue from his place in New York's St Regis Hotel in the 1950s.
Once acting as creches for toddlers who would one day be rich and powerful - the late Jimmy Goldsmith spent his childhood in a variety of swanky establishments - most English hotels are far less willing to take on long-term customers than they were at the beginning of the century. A few years ago low-spending pensioners were blamed for the financial difficulties at the Savoy, which stopped taking full-time residents relatively recently.
'The rich used hotels as an alternative to nursing homes,' Jeremy Logie, chief executive of the British Hospitality Association, told one newspaper. 'But they used to complain a lot and didn't spend much money, so most establishments did not replace them when they died. The only people who live in London hotels now are the incredibly wealthy.' Which brings us back to Robinson, for whom this highly expensive suite is little more than a diversion from his other retreats.
He also owns several very handsome properties. His main home, Orchards in Surrey, was built in 1897. There is a more recent buy in Hampshire. Both of these have gardens designed by Gertrude Jekyll. And then of course there is his highly controversial Tuscan villa, which Blair so presciently declined to patronise in 1997.
But as with everything in Britain, there are classes of extravagance. In June the Europa Hotel at Gatwick airport announced that a Ford car salesman had just checked out after a three-year stay.
Alan Edgington, 37, had moved to Crawley from Plymouth and started using the Europa as a temporary base. But when he did his sums he discovered that, once he had paid his bills and rent, he would be better off at the hotel. When friends asked him if he had found somewhere he said: 'Yes, I've got a mansion with a 100ft pool, a gym, a bar and a maid for £1,000 a month.'