Star Trek has always had an optimistic view of the future. There's little a well-trained Starfleet Medical doctor can't do if he or she just has a good tricorder.

Medical science has progressed so far as to make our hospitals seem barbaric and in a universe where a doctor can replace your entire spine if necessary, everyday aches and acne are as nothing to them.

Life at this cutting edge of space medicine, though, has somehow seen off eight doctors in just four series.

On the original Enterprise, Dr Boyce used to tuck a hip flask of alcohol into his medical bag, this being what Captain Christopher Pike needed at the end of a day. Not that Boyce was a whisky man necessarily, but as with all the doctors he was concerned about the Captain's physical and mental wellbeing. If the Captain can't cut it, it's the doctor who can relieve him or her of command.

His successor Dr Mark Piper might have felt the same, but he was swiftly succeeded by the great Dr Leonard McCoy (who was not above sneaking illegal Romulan ale to the Captain).

Still, close though Bones McCoy and Captain Kirk became, the closest of all the relationships was Captain Picard and Dr Beverly Crusher's, where we knew long before they did that they fancied each other something rotten.

That didn't stop her taking a year out to work at Starfleet Medical Headquarters, mind, and lumbering Picard with a stand-in, Dr Katherine Pulaski. Of all the doctors in all the series in all the worlds, she had to come in grumpy and though they worked together well, Pulaski never became quite the confidante that her predecessors did.

She set a trend, too, as Dr Julian Bashir took a long time to become close to Commander and then Captain Benjamin Sisko on Deep Space Nine - if he ever did. But there Bashir was far less experienced than any other human doctor in Star Trek and Sisko had his old friend Dax to rely on.

We'll never know how well Star Trek's seventh doctor would have got on with his Captain as he was killed at the start of Star Trek: Voyager and missed all the fun. Ironically, that doctor was never named - and his electronic replacement, the Emergency Medical Hologram would only ever be known as 'The Doctor' too.

Voyager's Doctor is a summary of all the doctors who have come before him - both literally as his programmed knowledge he is the sum of many doctors' experience - and also dramatically. Initially he had Bashir's inexperience, Pulaski's lack of bedside manner and also the same moral distance, the same viewpoint and ability to support the Captain as McCoy and Crusher did.

Key Doctor episodes: Boyce - The Cage (TOS); Piper - Where No Man Has Gone Before (TOS); McCoy - For the World is Hollow and I Have Touched the Sky (TOS); Crusher - Remember Me (TNG); Pulaski - The Child (TNG); Bashir - Hippocratic Oath (DS9); The Doctor - Real Life (VOY)