Kevin Federline is apparently holding Britney Spears to ransom over their divorce by threatening to sell a video tape of them having sex.

According to a report in the News Of The World, Federline has already been offered �26 million for the four-hour long sex-tape, supposedly filmed weeks into their relationship.

Now Federline is demanding Britney gives him a �16 million pay-off PLUS custody of their two young children, after she filed divorce papers on him last Monday.

A source tells the paper, �This vid is dynamite and Kev knows it. He has told Britney she should comply with his demands otherwise the whole world will see her having sex, which will be devastating.

"At the time the two of them were in the honeymoon stages of the relationship and couldn't keep their hands off each other.  They did nothing all day but have sex - and play the odd game of chess.

"They were insatiable and they believed they would be together forever. Britney didn't think twice about making the video at the time. She mistakenly believed that their love would last.�

Shocking news... they actually played chess?