By City A.M. Reporter The napkin which secured footballer Lionel Messi’s move to Barcelona more than 20 years ago has been sold for £762,000. The unusual document, which became legendary in the sporting world, was offered at Bonhams with a starting price of £300,000 in an online auction which ended on Friday. The napkin, described by Bonhams as a “standard Spanish waxy napkin”, contains a pledge that the young Argentinian footballer will be signed by the club at an agreed fee. Ian Ehling, head of fine books and manuscripts at Bonhams New York described the sale as “wonderful”. He said: “Since …