Valentine's Day, our annual celebration of love and romance - and a bonanza for greeting card manufacturers, florists and chocolate manufacturers - is rooted in fact and legend that are rather less joyful than the atmosphere February 14th is meant to encourage.

The Roman Catholic faith recognises at least three different saints going by the name Valentine, or Valentinus, all of whom met premature ends as martyrs.

One story goes that Valentine was a Christian priest in third century Rome. Though Christianity did not become the official religion of the Roman Empire until the beginning of the fourth century, it had already made great inroads and priests like Valentine were able to practise their faith and preach.

When the Emperor, Claudius II, a successful and occasionally brutal general with far-reaching military ambitions, reached the conclusion that single men made much better soldiers than those with wives and children, he banned marriage for young men.

Valentine, considering this decree to be wildly unjust, continued to perform marriages, but in secret. Young lovers would be joined in matrimony, sure that what God had put together no man would put asunder, and that new husbands would not have to go off to war.

Unfortunately, Valentine's undercover wedding work was discovered, and enraged Emperor Claudius ordered that the priest's head should be sundered from its body.

Claudius seemed to have a thing about priests with this name. Some scholars believe that the original Valentine was actually a bishop called Saint Valentine of Terni.

He too would end up beheaded on the orders of Claudius II - or Claudius Gothicus to give him his full title.

Perhaps it was all this beheading that inspired the idea that the madness of love can be described as 'losing your head'.

At least there is a Valentine from the past who wasn't decapitated, though his story doesn't end too well either.

It's suggested that this Valentine was a caring soul outraged by the treatment meted out to the inmates of Roman prisons, where torture and beatings were commonplace, and he resolved to do something about it and help prisoners escape. As a result, he ended up in prison himself.

It was here, the story goes, that Valentine sent the first message inspiring the tradition still going strong today. The prison's gaoler had a daughter, who was blind. Valentine fell in love with her and miraculously restored her sight, later sending her a love note signed: 'From your Valentine'.

Sadly, though he both lost and kept his head, lovestruck Valentine died in custody.

However, it is also stated that Saint Valentine of Terni also cured a young woman's blindness and sent her an affectionate note, so it is clearly possible that the two stories are versions inspired by the telling of tales about just one man.

There is another theory about the origin of Valentine's Day which does not involve the grisly death of a man called Valentine.

It may well be that the early Christian church decided to put its own gloss on a popular pagan event called Lupercalia. Celebrated in February, this celebration was a fertility ritual dedicated to Faunus, the Roman god of agriculture, and Romulus and Remus, the mythical founders of Rome raised by a she-wolf.

The festival survived the rise of Christianity, but was perhaps subtly modified until Lupercalia itself was outlawed at the end of the 5th century - when Pope Gelasius also named February 14th as St Valentine's Day - allowing a different kind of celebration to take its place.

From then on, facts, legends and rituals blended and fused until the month of February, and one day in particular, were associated with love and romance, the sending of cards, and the buying of all those flowers and chocolates.