David Turnbull made it 3-0 with an excellent strike from distance. The Scottish midfielder took a touch before unleashing a swerving effort that left Alnwick in the St Mirren net with no chance.
Celtic have been at their irresistible best today, scoring three goals in the opening thirty minutes.
Earlier, a brace from Liel Abada sandwiched the sending off of Power after he fouled Turnbull on the touchline. The Celtic midfielder clearly has had the last laugh.
Jim Goodwin will be hoping his Celtic TV stream can crash otherwise it could be a long afternoon for the isolating Saints boss.