Boris Becker may have lost his £100m fortune in part because of questionable investments in the Nigerian oil industry, according to claims in the German press.

Since the 49-year-old former tennis star was declared bankrupt in a London court last month, speculation has been rife over how he managed to squander a personal fortune estimated at over £100m.

Now Germany’s Spiegel magazine has published claims that Mr Becker’s business dealings went far deeper than celebrity endorsements and media appearances.