When it opened in 1964, the Post Office Tower (known today as the BT Tower) was not only Britain's tallest building, but the first in London to have a revolving restaurant at the top. The film above, an episode of 'Look at Life' produced in 1966, shows it in operation.
The revolving restaurant (operated, improbably, by Butlins) was closed in 1980 due to security concerns, and seems unlikely to re-open, despite rumours that it might. Revolving restaurants have gone out of fashion but if you're looking for a table with a view, try SushiSamba or Duck & Waffle in the Heron Tower, or the new restaurants in the Shard, or else wait until next year when 20 Fenchurch Street opens — an image of its 'Sky Garden', complete with a three-level restaurant, was released earlier this week.
(Hat tip: Modernist Estates)