While he accepted a five-year term he privately told friends he doubted he would remain to the end, having seen too many chief commissioners stay too long.

He planned to go in March next year, but with the change of state government he considered pushing the date back a few months to avoid the perception that it was a political decision.

The recent death of his father and his mother's battle with serious illness left him determined to plan for life away from the all-consuming job.

When I asked him a few weeks ago about his future plans he ducked the question, then added: "have other things that I want to do with my life."

He planned to work though the bush-fire season before announcing his departure. But the recent discovery that Chris, his wife of 33 years, was also ill and faces 12 months of treatment led to Monday's resignation announcement.

While he will leave office at the end of January he has gone on leave and will not return to duty.

In many ways this reluctant chief commissioner has been a remarkable one.

When his predecessor, Simon Overland, was forced to resign, the police force was in chaos, with infighting in the command team, vicious battles with the powerful police association and chronic media leaks that created juicy headlines.

Lay, then a deputy commissioner, had already decided to quit. He sold the family home and he and Chris planned to move overseas to a senior law enforcement posting.

But when Overland stood down and after much thought, Lay applied and was appointed chief commissioner.

He was seen as the safe option. A local cop with an easy manner, his brief was to steer clear of controversy.

History will prove he was much more than a pair of safe hands.

First he healed, rebuilding the relationship with the police association through his strong friendship with then secretary Greg Davies.

He tried to avoid mindless media spin. As a former assistant commissioner for road policing he saw the media as a potential tool to get his message out to the public rather than an enemy looking to try to trip him up.

Then, through a series of resignations and retirements he was able to pick his own command team. As he said: "It was a greenfield site and I was able to pick people who covered my skill gaps."

Equally important they proved to be loyal, and the leaking stopped. Having righted the ship Lay quietly set his own course.

Perhaps because he wasn't desperate to be chief commissioner it gave him the freedom to be his own man.

He said what he thought, not what he thought the government of the day wanted him to think.

At a time when politicians were promising more police stations in swinging seats, Lay quietly pointed out they were living in the past, investing in a 1960s model of policing doomed to fail.

"You open a police station and police just disappear inside. People want to see the light on in their police station but the reality is they rarely come in. We will have to explain to the community this is about providing a better service."

A career cop not caught in the past he invested in a planning model on how the force should look in 2025. He didn't want more cops but more experts, more taskforces and smarter strategies.

"We can't arrest our way out of our problems. Perhaps it is time that we changed the debate to get smart on crime."

Lay is proud of the role he has taken on confronting family violence but one of his greatest legacies will never be seen in the crime statistics.

It concerns that overused word, culture.

He started work on dealing with police depression, a massively underestimated problem. He has also launched a taskforce to deal with sexual harassment in the workforce, freely admitting there are predators who have been intimidating junior female staff. "This is a major failure in police culture. It is bullying of the worse kind," he said.

Part of a chief commissioner's role is to provide potential successors from within the ranks.

Certainly the government will be looking for a chief commissioner who believes in evolution not revolution and will be inclined to steer away from potentially controversial choices.

Premier Daniel Andrews will be determined not to return to the days when police infighting dominated the headlines.

This will give Lay's deputies Graham Ashton, Lucinda Nolan and Tim Cartwright the inside running, although NSW Deputy Commissioner Nick Kaldas has some support. But it is too early to guess and there is always a chance of a bolter.

After all, Ken Lay was the outsider who turned himself into a favourite.