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
Tuesday evening's weather for the west of the region
Tuesday evening's weather for the east of the region
A man has been cleared of smuggling 35 immigrants in to the UK in a container. One immigrant, Meet Singh Kapoor, died during the journey.