By Elliot Gulliver-Needham “Sell in May and go away, don’t come back until St Leger’s Day”. The phrase is an often quoted investment adage, referring to the St Leger’s Stakes, a horse race run in Doncaster and a four-day meet during the middle of September, with horse racing often being a favourite pastime of the financial world. “The theory behind the idea probably stems from the time when trading was an in-person activity, which took place on the floor of the stock exchange,” explained Victoria Hasler, head of fund research at Hargreaves Lansdown. “Investors were often wealthy individuals wh…