SPL - Celtic sink battling Saints
Saints more than matched their opponents in a first half of nip and tuck, but Gary Hooper would have impressed the watching Premier League scouts with a 30-yard dipping snapshot that pulled a full-length save from Craig Samson.
Saints' new signing Dougie Imrie was a handful all afternoon but the unmarked Paul McGowan missed the hosts' best chance of the match shortly after the restart with just Forster to beat, shooting straight at the keeper.
Kenny McLean and Imrie had both previously tested Forster and inevitably, the Buddies' missed chances came back to haunt them.
There was 71 minutes on the clock when a Kris Commons free-kick was punched out to Brown, who laid on a perfect ball for Forrest to lash home.
And the game was put beyond doubt with two minutes remaining.
A short corner gave Brown time and space and he curled a superb strike beyond Samson and into the corner.