Thousands of gay and bisexual men convicted of now-abolished sexual offences have been posthumously pardoned.
The historic moment was confirmed by the Government as the so-called "Turing's Law" took effect on Tuesday.
Justice Minister Sam Gyimah said it was a "truly momentous day".
The pardons, which were first announced last year, have now been officially rubber-stamped after the Policing and Crime Bill received Royal Assent.
It enshrines in law pardons for those convicted of consensual same-sex relationships before laws were changed.
There were calls for wider action after Second World War code-breaker Alan Turing was given a posthumous royal pardon in 2013 over a conviction in 1952 for gross indecency with a 19-year-old man.
Turing was chemically castrated and died two years later from cyanide poisoning in an apparent suicide.
Mr Gyimah said: "This is a truly momentous day. We can never undo the hurt caused, but we have apologised and taken action to right these wrongs.
"I am immensely proud that Turing's Law has become a reality under this Government."
The new law will also see statutory pardons granted to the living.
However, this will only apply in cases where individuals have successfully applied through the Home Office's disregard process to have historic offences removed.