(Reuters) - Hargreaves Lansdown's largest investor Peter Hargreaves will sell shares worth about 500 million pounds in the British investment platform via a sale to institutional investors, a bookrunner on the deal said."This is part of a process of long-term financial planning to diversify my assets. I remain, and will continue to be, a substantial shareholder in Hargreaves Lansdown," Hargreaves, who co-founded the firm with Stephen Lansdown in 1981, said.The sale will come just days after a..