The 65-year-old Olympian - who was known as Bruce Jenner before her gender transition - has reportedly landed the ''biggest paycheque ever'' for a solo reality series on E! and the deal is worth much more than the network initially wanted to pay.

E! - who also broadcast 'Keeping Up With the Kardashians' and its spin-offs - initially offered $2 million but were forced to up their offer as they feared losing the rights to the eight-part 'I Am Cait' series to another network.

A source told RadarOnline.com: ''It's the biggest paycheque ever given by E! for a solo reality show, and Caitlyn's agent was relentless in getting her the huge payday.

''At one point, talks between the network and E! had broken down, because nobody wanted to pay her more than $2 million. Caitlyn's agent then began informal talks with other networks, and E! quickly came back to the table, ready to pay $5 million.''

A spokesperson for E! refused to confirm or deny the figures.

The representative told the New York Post newspaper's Page Six column: ''We do not comment on financial matters. Caitlyn will share her story when 'I Am Cait' premieres on July 26.''

While Caitlyn will receive a huge sum for the show, it is dwarfed by the $100 million agreed by her ex-wife Kris Jenner in recent contract negotiations with E!.

The showbiz matriarch - who also manages her children's careers - agreed the four-year deal for new series of 'Keeping Up With the Kardashians' and its spin-offs, and the money will be split between her, daughters Kim Kardashian West, Khloe and Kourtney Kardashian and Kylie and Kendall Jenner, as well as Kourtney's boyfriend Scott Disick.