ITV said the programme was the highest rating show of the year so far, nudging ahead of a Coronation Street which pulled in 11.2 million in January.
Adding viewers for ITV's +1 channel brought the audience to 11.9 million for the BGT finale, with a peak audience of 14.5 million.
More top news
Holly has all your up-to-date weather details.
Those over 60 are being encouraged to get down to their sports centres to keep fit
Scientists are trying to identify an unusual hairy crab found washed up on Chesil beach in Dorset.