Ex-police chief Richard McCreadie said that in 1970 he was about to arrest headmaster David Lawrence and music teacher Ronald ‘‘Mousy’’ Thomas after they confessed to sexually abusing a former student.

But before he could charge the pair, Lawrence resigned and went to the UK and Thomas fled to South Africa, Mr McCreadie told the Royal Commission into Institutional Responses to Child Sexual Abuse.

Mr McCreadie only came forward with his story this week after the school gave a conflicting account of Lawrence’s abrupt departure.

Mr McCreadie said he was a junior detective with the sexual offences unit when a former Hutchins student complained of being sexually assaulted by Lawrence and Thomas on multiple occasions.

He said both men confessed to the crimes when interviewed.

‘‘Lawrence immediately admitted to that having occurred. I was somewhat surprised that he was so candid about it,’’ Mr McCreadie said.

But Mr McCreadie said that when he went to have the men arrested and charged, he was told by the school that they had both gone overseas.

‘‘At that time, it would have been very unusual to extradite anyone from overseas unless they had been charged with murder,’’ he said.

‘‘It is my view that the government at the time would not have approved the costs of an extradition of Lawrence and Thomas.’’

He said he did not discuss the matter with anyone else at Hutchins, and was uncertain about what had happened to his notes from the time.

Mr McCreadie said he felt compelled to make a statement after hearing that the school believed that Lawrence had left because his secretary had opened a sexually explicit letter from a former student.

Current Hutchins headmaster Warwick Dean told the commission that the school had received nine complaints of historical abuse this year, none of which had been finalised.

Mr Dean said the school should have been quicker to acknowledge the abuse of a former student known as AOA, who first came forward in 1993, but did not receive an apology until last month.

‘‘Knowing what I know now and having made the apology to AOA, I think that it might have been something that could have been considered,’’ he said.

‘‘It’s in my nature to be the person who says if this is wrong, it’s wrong, and I’ve never held back on an apology.’’

The Hutchins hearing will continue in Sydney on December 18.

■If you need support contact Relationships Australia on 1300364277 or the Sexual Assault Support Service on 62311822.