It's Tuesday, and I am sweating my way around the suburbs of Havana. Along with a cameraman and producer-cum-director, I'm here to author a film for Newsnight about the wonders of Fidel Castro's medical system. Cubans may still be denied such trifles as free elections, but they have perfect teeth, and in the whole city, there seems to be only one obese person.
So, we visit surgeries and clinics, and Havana's cutting-edge biotechnology campus, where "Frankenstein" machines - made up of 20-year-old hardware, mixed up with ad hoc modern components - whirr away, playing their part in the development of a mind-boggling array of vaccines and drugs. Among them are three anti-cancer treatments which are so trailblazing that the US authorities have decided to make an exception to the economic embargo and allow the American firm CancerVax to sign a multimillion-dollar contract.
A very different innovation is the 120 Club, a nationwide association open to anyone who fancies notching up six score years. Fidel turns 80 in a couple of weeks; his personal physician has recently claimed that he will set the country an example by making it to 140. For ordinary Cubans, there is only one problem: if you were born before 1955, state-subsidised cigarettes can be part of your weekly rations, working out at roughly one US cent for 20. When I meet the vice-president of the 120 Club, the question has to be asked: how do absurdly cut-price fags square with the national obsession with preventive medicine? His reply demonstrates a very Cuban logic. "My advice is this - get the cigarettes, but don't smoke them."
Lennon's capitalist philosophy
One of Havana's newest and most popular tourist attractions is Lennon Park, built around a statue of the ex-Beatle and opened in 2000 by Castro, who claimed that he "shared Lennon's dreams completely". Really? Aside from a brief run of fairly useless protest songs, Lennon lived his life as an unapologetic capitalist - proof that, despite its eternal fondness for radical chic, the music business is a case study in the kind of free-market economics at which Fidel would presumably blanch. Take, for example, a choice moment from the Beatles' first US press conference in February 1964. "Will you sing for us?" begged one journalist. "No," Lennon barked back. "We need money first."
Absolutism is back
When I last came here in 1998, the authorities' frostiness towards private enterprise was beginning to show signs of a thaw. Now, buoyed by money from China and Venezuela, they have swung back towards old-school absolutism: no new joint ventures with foreign companies have been agreed in the past year, and even getting a licence for a small restaurant is very difficult, apparently. As far as the Communist Party is concerned, even small business people are always in danger of turning into ethical monsters.
Tommyrot, I'm saying. Two years ago, exiled from the capital by the prohibitive price of even a small flat, my girlfriend and I bought a house in Hay-on-Wye. It came with its own shop, now an outlet selling cookbooks and kitchenware. On the occasions when I put in a few hours, the obligation to 1) talk to strangers and 2) secure money that might otherwise go to Tesco suggest progressive values in excelsis - as happened the other week, when a couple from Birmingham came in. Given what was on the shop stereo, he joined me in a long conversation about the recent death of Syd Barrett; and she bought a wooden spoon. This is surely the kind of heart-warming stuff that members of the Fabian Society call "social capital".
One last thing. Just before I left for Cuba, I took part in a brief radio debate about David Cameron's very sensible plan to put a rocket under the UK's democracy by opening the selection of the Tories' next London mayoral candidate to a US-style open primary. A participatory website is obviously in order - so, pilfering an old bit of William Hague wordplay, myself and a few friends have already registered a nice domain name: londontorynightmayor.co.uk
John Harris's Newsnight film will be shown on 1 August (BBC2)