Justin Welby's son has spoken about his father's resignation last week under a cloud of consternation after he failed to ensure that sadistic abuser John Smyth had been reported to police.

The Archbishop of Canterbury resigned on Tuesday after days of intense pressure following the publication of the Makin Review into decades of "abhorrent" abuse by the late Smyth, a QC who used to organise evangelical camps for boys. 

The review found that Smyth had abused at least 115 boys and young men across the UK, South Africa and Zimbabwe, and that Welby was aware of it from at least 2013 but failed to act. In a scathing assessment of the wider Church's response, the Makin review said there had been a "cover-up". 

Welby later denied a cover-up but admitted to "incompetence", and in his resignation statement said that he "must take personal and institutional responsibility for the long and retraumatising period between 2013 and 2024".

Speaking about his father's decision to step down, his son Tim Welby told the Mirror that he had done the right thing and that his position had become "untenable" because "so many people were calling for his resignation". 

He said his father was "really, really cross that it didn't occur to him to triple check" that someone had reported the abuse to police.

"The frustrating thing is I don't think it ever occurred to him that it hadn't been reported to the police," he said.

"When, as Archbishop, you are told that something has happened it has usually gone through so many hands. It seemed utterly inconceivable that someone wouldn't have said to the police: 'This has been going on.'"

Despite his failings, Tim Welby said he was "proud" of his father and loved him very much. He said his dad would spend his remaining time in office meeting victims and trying to put measures in place to ensure mistakes are not repeated.

"He's definitely very embarrassed and appalled by what's happened. I know he's going to spend a lot of his time left in office, having conversations with some of the people and trying to make sure that things are set up in the right way," he said.