Joe Salisbury and Harriet Dart clinched Battle of the Brits victory for their team after beating Jamie Murray and Heather Watson in a winner-takes-all decider on a thrilling final day.
Salisbury and Dart won 6-4 6-2 to seal a 63-56 win for the British Bulldogs.
Union Jacks pair Andy Murray and Naomi Broady set up the deciding rubber by winning the penultimate match of the week-long tournament in Roehampton.
But Jamie Murray and Watson could not capitalise as the Bulldogs celebrated.
With the sides tied at 45-45 going into Sunday, each team won five matches on the final day - but the Bulldogs won the matches worth more points in an innovative format.