Sky and ITV reportedly thought that they had secured the rights to cover Champions League football from the 2015-16 season before BT Sport made a late swoop for the landmark deal.
Both broadcasters are said to have initially agreed to pay £800m between them after being approached by UEFA's marketing agents TEAM.
While all parties were under the impression that a deal had been sorted, a breakdown in communications occurred, allowing BT Sport to secure a 24-hour negotiation period, according to the Daily Mail.
BT's deal, which is said to have cost the broadcasters close to £1 billion for a three-year package, was announced on Saturday.
It is the first time that one single broadcaster in Britain has won the rights to air European football, including the Europa League.
