Some historians believe one of the first Valentine's card was written by a Frenchman while he was in London
It was in 1415
He was not in London for a visit. Actually he was staying in the Tower Of London, where he was a prisoner.
He was captured after the Battle of AGINCOURT, the battle between the two armies of King Henry V and the French King Charles V (the battle of which you can read in Shakespeare's play, Henry V)
He was the most important and valuable capture of the day and was treated with all consideration
He was kept prisoner for 25 years until a ransom was paid in 1440 but during his captivity, he could enjoy many things normal prisoners didn't usually enjoy !
And to pass the time in his cell, he kept writing poems and romantic letters .. some to his wife ...