He graduated from Oxford University, where he was a Blue, in 1994 and had by then cemented his spot in the side as an opening batsman.
In 2007 Sussex won their third championship in five years, Montgomerie scoring 1,000 runs at 40.00 and taking 27 catches.
One of the most reliable and consistent county openers of his era, in 251 first class matches he scored 14,337 runs at an average of 35.84.
In the latter part of his career he often fielded at silly point and short leg, taking many catches for Mushtaq Ahmed.
He is currently a chemistry teacher at Eton College where he was a housemaster at Jourdelay's for 1 year, and is currently master in charge of the cricket XI.