The hosts had already gone close a couple of times before Hilson hit a post in the 24th minute, and it took the Red Lichties just three more minutes to go ahead as O'Brien struck with a deflected long-range effort.

Arbroath doubled their lead in the 36th minute when Hilson tucked home the rebound after Bobby Linn's shot had come back off a post.

Dunfermline had the wind behind them in second half but they could not make any headway against their hosts and have now won just once in six matches, dropping to third in the table in the process.