Irwin is only a few years older than the boys. Employed specifically to get the boys into Oxbridge, he pretends to have been to Oxford.
He teaches the boys to approach history in a way which can be seen as a game – taking an original approach by simply arguing the opposite to what the normal belief is. They take it as a game, seeing an opportunity to show off the facts which Mrs Lintott has taught them. But Irwin believes it can lead to greater truth, in that it forces them to think more deeply.
We see that he becomes a spin doctor and then a presenter of a TV history programme. This suits his apparently flippant and glib attitude to education.
Inappropriately, Irwin is attracted to Dakin. He does not want to be like Hector, but does not reject Dakin's offer of himself to him. Irwin is different to Hector in that it seems the boys have power over him, both in the lessons, and when Dakin approaches him.
Irwin is not a very sympathetic character: his cynical side is emphasised from the opening scene, as a spin-doctor. He does not help Posner when he confesses his troubles with Dakin. But he gets the boys into Oxbridge.