One of his deliveries could conceivably have been a cutter. Bowlers can use their index and ring fingers to spin the ball from leg to off. It's easy enough to control and the ball sometimes cuts quite a lot off the pitch for a seamer.
In addition to this, one can have a lot of variations- a quicker ball, an inswinger or outswinger, an off-cutter. But the leg-cutter would have been the one that noone else bowled, hence the one everyone remembered. In particular, it could have been one or two high-profile incidents where the ball broke heavily off the pitch that gave a lot of onlookers the impression of a fast leg-break bowler.
I'm only speculating, of course. It's all anyone really can do, given the information available.
Originally Posted by zaremba
The Filth have comfortably the better bowling. But the Gash have the batting. Might be quite good to watch.