Lack of proof that he is here legally is not proof that he is here illegally.

Maybe not, but not having proof of status will get you expelled and not just under the Tories and not just in Britain.

It is in many cases perfectly possible to prove the circumstances of a migrant's arrival in this country,

No problem in that case, but the Windrush children were left with nothing.

In the case of the Windrush generation that was prima facie evidence of their legal status here.

What was? There was no evidence of their boarding or landing. It was decided to burn those records in 2009.

Most children had nothing to show how they got here, or that they were entitled to say.

In some cases perhaps it might be seen as difficult or even impossible to find proof of someone's illegal status. In that case their right to stay would be recognised

No it would not. That would make it impossible to remove any illegal immigrant. There is no way to prove that anyone arrived illegally. It would be an automatic and immediate amnesty for everyone as soon as they stepped off the lorry or boat.

But it was fundamentally unjust, as the government now belatedly admits.

The government never denied it. It is obviously unjust that those people were left without proof of status. No one government is to blame for that injustice.

There are estimated to be over a million illegal immigrants in Britain.