The Pilgrims are going up after their 2-1 turn around victory at St James Park.
Ian Culverhouse’s team have done it the hard way with three wins on the road but the sweet taste of Promotion Final success was sealed in the second half.
Jimmy Knowles’ penalty got the party started - and Boston were full value for from the moment they levelled just before half-time through Keaton Ward.
The Saints went ahead through Morgan Roberts but it wasn’t to be again for Brackley.