Tonight's TV highlights

Diagnosis Live From The Clinic 8pm, Channel 4 Medical records and doctor-patient confidentiality are considered sacrosanct, so it's strange indeed that this new series takes the Embarrassing Bodies formula even further, inviting viewers to call in for an "appointment" with doctors Christian Jessen and Dawn Harper, who will then diagnose the cases they're presented with live on air. There is also general medical advice, but just how far will it go? And what's next? Live confessions with a celebrity priest, who dispenses handy hints on being a good Catholic? David Stubbs Heath v Wilson: The 10-Year Duel 9pm, BBC4 To contemplate a sequential list of British prime ministers is to marvel at the caprices of the electorate: if a single person's convictions lurched from Churchill to Attlee to Eden in a comparable timeframe, they'd be certified. Few contrasts, however, have been as stark as that between Edward Heath, who occupied No 10 between 1970 and 1974, and Harold Wilson, who served before and after him. Their rivalry was as personal as it was political, and conceivably made a grim period in British history grimmer than necessary. Those who endured their rancour at close quarters tell the story. Andrew Mueller Megastructures 9pm, National Geographic The 1,000km Qinghai-Tibet railway passes through terrain so hostile that its construction was likened to "building a railway on Mars" and indeed, some 3,000 workers died of exposure while working on it 50 years ago. Today, it's nothing short of an engineering miracle, built to survive freezing temperatures at altitudes higher than the Swiss Alps. Train-obsessed Finnish engineer Pasi Lautal is our unofficial guide on this remarkable journey, rumbling through the ghostly Tanggula, the highest railway station in the world, and on to the $35m Lhasa station. Ali Catterall The Apprentice 9pm, BBC1 Lord Sugar has dispensed with three "entrepreneurs" already, and, after last week's fancy shopping task, he's testing the remaining candidates' sales skills by asking them to set up a beauty business in Birmingham. (The producers, one imagines, must have been feeling alliterative.) It's been a solid run of boys getting the chop so far, so it could be dangerous for the girls tonight. Rebecca Nicholson The Office: An American Workplace 10pm, Comedy Central We remain a season behind the US run of The Office, which means we have Steve Carell's Michael with us for a while yet. Tonight, Michael is persuaded by Dwight and Andy that a salesman is a member of the mafia, despite Oscar's best efforts to suggest that it might not be the case. Predictably, mayhem ensues, as Jim and Pam's honeymoon is ruined by both this and the use of Jim's office as a fart station. RN Stewart Lee's Comedy Vehicle 11.20pm, BBC2 "This isn't a mistake, this is my act!" Stewart Lee's self-deprecation is second nature and he remains as dry as the Atacama desert. Here, he happily tests the limits of the shambolic while pulling the rug from underneath what is now accepted as comedy. He sets out to do a musical comedy routine so as to win over the audience but can't resist a few nice barbs about Michael McIntyre's Comedy Roadshow. The risk is that he deconstructs comedy to the point of nihility – the interview scenes with Armando Iannucci are particularly grating and unnecessary – but Lee is such a pro he always let's the joke, in some form, get through. Martin Skegg