Theresa May's legacy will be that she fought the law and the law lost

In the 75 days she has left as Home Secretary, Theresa May has one important piece of unfinished business.

It will involve her returning to the subject – police reform – that has won her plaudits for her courage in standing up to vested interests and for driving through change where her predecessors were reluctant to act.

She stunned the Police Federation by telling its conference last year that the legitimacy of policing was in jeopardy following such scandals as the Stephen Lawrence inquiry and the alleged cover-up of the Hillsborough tragedy.

She coupled her damning assessment with a warning to the federation, effectively the trade union for rank-and-file officers, that the time had come for it to modernise its operation.

Her tough stance attracted admiring headlines for her willingness to take on vested interests and intensified claims that she possessed the inner steel to lead the Tory Party.

Since then events have crowded in for May, including heightened fears of terrorism, turbulence in the immigration system and the shambles of the historic sex abuse inquiry.

But she has not abandoned her mission to overhaul policing and is determined to push through her promised changes before Parliament is dissolved for the election in around five weeks’ time.

With the number of complaints against the police increasing by 50 per cent in the past decade, her reforms are designed to rebuild trust in the integrity of British policing and to make it easier to root out corruption among officers.

The new measures will force the police to hold disciplinary hearings in public with a legally qualified chair and will end big pay-offs to officers found guilty of corruption.

They will also strengthen protection for whistleblowers by making it a disciplinary offence to take reprisals against them.

She has also given the go-ahead to a wide shake-up of the Police Federation following a damning report that concluded that the wealthy organisation was financially unaccountable, politically “wrong-headed” and riven by “distrust and division”. The moves include forcing the federation to open up its books and banning compulsory membership.

For a while it appeared that May had run out of parliamentary time to force the complex changes through, but she received a crucial boost when Home Office lawyers advised her that the changes could be introduced without major legislation.

One colleague explains: “She is really, really focused on this and wants reform to happen. The subject gets her very fired up. She wants to be able to point to concrete action rather than talk.”

Underlining that determination, May returned to the subject of police failings this week when she warned forces that members of the ethnic minorities were still being disproportionately targeted for stop-and searches. She warned that a Tory government “will not hesitate” to legislate to reform the controversial powers if their misuse continued.

That record – combined with the latest measures about to come into effect – will allow her to portray herself as a reformer intent on reversing the steady erosion of public trust in the police.

There is no doubting the sincerity of her crusade, but it is also a useful story to tell if the day comes to pitch for a bigger job than Home Secretary.