Former tennis star Boris Becker, who was declared bankrupt in a London court last month may have lost his £100m fortune in part because of questionable investments in the Nigerian oil industry, Telegraph reports.

Germany’s Spiegel magazine claims he made investments in the Nigerian oil and gas industry, and at one point considered a single investment of more than $10m (£7.6m) through Forbes & Manhattan, a Canadian investment bank and a former associate of the tennis player, according to documents it was shown.

They include what purport to be internal emails from Doyen Global, a sports management agency which represented Mr Becker for a brief period starting in late 2013, which reportedly show that Becker Private Office, a company controlled by Mr Becker, held extensive shares in the Nigerian oil and gas business which went bust.