“Welcome to the human race, John Soames. Go on, let it out. It was never easy being born.”

Until now, when people compiled lists of horror films by Hammer also-rans Amicus, The Mind Of Mr Soames was never mentioned. Described simply as "well intentioned" by Jonathan Rigby in his exhaustive tome English Gothic, and steadfastly ignored by pretty much everyone else, Soames may be more sci-fi than outright horror, but I'd contend that there is horror there - it may even be the studio's only stab at putting the Frankenstein story on-screen.

Set firmly in the groovy Amicus-land of the late 60s, Soames is also the perfect antidote to the rest of the company's output of the time (Scream And Scream Again etc) in that it's thoughtful rather than stoopid, languorously paced and rather charming.

John Soames (Terence Stamp) is a man who has been in a coma since birth, meaning that although his body has fully matured, his mind has never been stimulated. Kept alive intravenously over the years, he lies in a glass coffin in a cold, sterile institute.

As his 30th birthday approaches, moves are afoot to wake him up. A specialist, Dr Burger (Robert "Man From Uncle" Vaughn) is brought over from LA, and the owner of the institute, Dr Maitland (Nigel Davenport), has arranged for the entire event to be broadcast live on television. In what is quite an accurate prediction of things to come in the real world, Maitland has decided that once awake, Soames' life will be played out in front of the cameras. Neurologists, scientists and surgeons from all over the world attend the "birth", with the TV commentator giving a running commentary on the operation: "The drilling is about to begin… to form an entry to the brain…"

When, following the operation, Burger is congratulated on a "good show", he begins to realise that Maitland may not have his patient's best interests at heart - but by then it's too late, and all they can do is wait to see if their "baby" will wake up. There's a real sense of wonder as we wait with them, too. And when it happens, it's brilliant - Burger telling the new arrival: "Welcome to the human race, John Soames. Go on, let it out. It was never easy being born."

Soames is immediately put on an accelerated learning programme, with his every move recorded for posterity. Maitland has set himself up as parent and teacher to the "child", but he refuses to allow Soames access to anything other than his carefully orchestrated programme. When Burger discovers this, he brings in a variety of groovy late 60s games for him to play (Buckaroo, anyone?) and then (horror of horrors) allows Soames outside to muck about in the garden. Soames (resplendent in his big pink babygrow) is having a high old time until Maitland discovers what is going on, sending loads of burly security guards out to drag him back inside.

This rough treatment has exactly the effect you'd expect - he's originally upset (heartbreakingly, when told he can go out again later, he replies "No. They will hurt me."), and then angry - twatting a security guard over the head (and killing him) to regain his freedom.

Soames is off and into the big wide world - a grown man wearing a one-piece pink suit and unable to string a coherent sentence together.

He finds a motorway ("red car!") and a pub, where he helps himself to a drink and a sandwich (very 60s choice - cheese or lettuce), but can't pay and gets kicked out. He then joins in a game of football with some kids (for "joins in" read "ruins"), and to top his big day gets run over by a drunk driver.

The driver takes him home (rather than admit to the authorities that he'd been drinking), and Soames wakes up in a strange bed. Up until this point no-one has recognised him, which seen in this day and age seems quite odd - after all, he'd be a celebrity in the 21st century. But the media have cottoned on (the Daily Mirror's headline is "Can this baby kill?") and the driver's wife recognises him.

"Poor Mr Soames, I don't know what they did to you," she tells him. "It was my useless, drunken husband that knocked you down. He's much more dangerous than you…"

He certainly is, because although she's on Soames' side, the husband has phoned the authorities and the fugitive has to do a bunk and is on the run again. This time he gets onto a train, where he terrifies a timid young girl by indicating he'd like her apple (shades of Horror Hospital there) and blathering on about "London is the capital of England" and "There are many trees in the institute… I do not like the institute." (I have to say that I'd be scared at this point - in fact, there's a point where you wonder exactly which way the film makers are going to take this).

Soames ends up cornered by the police, the media and the scientists in a rain-lashed barn, where the glimmer of a happy ending can just about be seen through all the darkness.

The tale is basically Hammer's take on Frankenstein without the stitched-together oaf - Maitland is the Baron, a cold and ruthless man uninterested in his "creation", despite giving him life. Burger is the more idealistic, thoughtful type of scientist, so often drafted in to help in Hammer's cycle of films - before the operation, he comments "Are you sure we should try to wake him? He looks happier than most conscious people…"

Soames is the "monster" - a child in a man's body, unable to control himself, confused and angry - and of course, eventually accidentally taking someone's life. He even takes refuge in a "blind" (she doesn't know who he is) woman's home until discovered, and if you substitute villagers for the TV crew and flaming torches for their spotlights, the parallels of this film's rain-soaked climax with the ending of many of Hammer's gothic fantasies are striking.

And it's worth mentioning that Stamp's performance throughout is extraordinary. What could be an appallingly embarrassing turn (grown people playing children rarely works) just isn't, somehow. It's a testament to the man's talent that at no point do you think he's anything other than 100 per cent genuine, whether he's making you laugh (the scene where he bounces a ball off Maitland's head is superb), cry (the moment before he makes his escape) or even just worrying you (the scene on the train).

The Mind Of Mr Soames is a dark gem, and a worthy pretender to the British horror hall of fame.