Viewed purely as a drama, this six-part serial for children filmed entirely on location in London in 1968 is risible as best. As a document of a halcyon time now long past, it’s enthralling.

Directed by Mike Hodges (whose better-known work includes the original Get Carter and the Queen-soundtracked movie version of Flash Gordon), the story follows three children who overhear a mysterious conversation in an old house and begin a citywide search for the mysterious Tyrant King of the title.

For six episodes, they visit London’s most famous landmarks in what is basically a poorly-disguised promotional film for the city with the slenderest of plots and a lot of hilariously cheesy dialogue chucked in for good measure. Back in the monochromatic day, it was probably pretty tedious. Now, sumptuously remastered in full colour from the original 16mm film material, it’s a stunning rendering of the capital in its most vibrant period.

According to the credits, the youthful principals were picked from the Italia Conti Stage School; and although Kim Fortune as Peter, Candy Glendenning as Charlie and Eddie McMurray as her brother Bill do their best to fit in amongst the groovy trappings, they can’t help but come across as pure Blyton: affluent, well-spoken and firmly rooted in a period long before tie-dyed t-shirts and flares ever made it to Carnaby Street.

Peter, as the eldest, is the stuffiest. ‘It’s all discotheques and clothes with you two,’ he moans at the outset, fiddling with his telephoto camera while his cooler chums read comics and listen to the radio. Quite how much clubbing 12 and 14 year-old siblings got up to in 1968 is unclear, but while Charlie and Bill have more costume changes than Madonna in Evita (as opposed to Peter, whose one notable departure from his sensible coat and trousers combo is a t-shirt proudly declaring him a member of the BBC West of England Light Orchestra fan club), their only genuine pretension to sixties hip are in Charlie’s daring miniskirts and Bill’s Brian Jones haircut and surly distrust of THE MAN.

‘They’d just tell us we’d be watching too much telly,’ he sneers dismissively when Charlie – for the umpteenth time – suggests that instead of visiting tourist attractions and constantly running into the mysterious Scarface (played by stalwart of ‘70s Doctor Who, Philip Madoc) they’d be better off informing the police of their quest.

However, this antipathy towards the forces of law and order could be due to a secret drug habit. At one point, Bill huffs on a plastic cushion as if it was a bag of glue; at another, upon being shown an innocent picture of a horse, he declares: ‘They look like Martians – or crabs!’

If that isn’t a pointer to a chronic pharmaceutical problem, his later exclamation of ‘What fantastic gear!’ is a dead giveaway. There’s even a coded reference to the ills of cold turkey when the villainous, Craig Revel Horwood-soundalike Uncle Gerry (sample dialogue: ‘Oooh, we are in a tizzy, aren’t we?’) locks him in a cellar. Brian Jones would be proud.

The founder of The Rolling Stones would probably be quite partial to the superb soundtrack, too. Although the Stones themselves only appear once (She’s a Rainbow) and the usual licensing difficulties preclude any appearances of The Beatles, there’s more than enough Cream (including The White Room and Sunshine of Your Love) and Pink Floyd (Interstellar Overdrive, Astronomy Domine and even Corporal Clegg) to satisfy the hungriest of nostalgia-rock appetites – although by the umpteenth time you’ve heard the Nice’s The Thoughts of Emerlist Davjack, even Brian might find himself reaching for the mute button. Like the endless shots of gleaming new London Transport buses, it’s massively overused. ‘Man, this is too much,’ Bill sagely observes.

Story-wise, The Tyrant King could have been wrapped up inside ten minutes. Happily, Thames (who were using the series as a trial run for the production unit that later became Euston Films, makers of The Sweeney) decided to stretch it out and leave us a vivid and gloriously prolonged portrait of London at its most swinging.

Released on DVD on Monday 14th November 2011 by Network.

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