Mr Richards, 49, was one of John Major's most trusted junior ministers. The speed of his resignation underlined the determination of the Prime Minister to crack down hard on ministers caught up in sex scandals.
There was no suggestion last night that his alleged affair with a 28- year-old divorcee breached security. But Mr Richards, a former desk officer for MI6, SAS and Special Boat Service reports at the MoD from1977 until 1983, still lists himself as a member of the Special Forces Club. He took a short service commission with the Royal Marines before becoming an intelligence officer.
Married for 19 years, with two sons and a daughter, he also listed the "family" with his interests. Mr Major made it clear after the Nolan committee report on ministerial "sleaze" and ministerial resignations that he would no longer tolerate ministers clinging to office.
The minister's swift resignation was seen as evidence of the tougher line. The Government's Chief Whip, Alistair Goodlad, spoke to Mr Richards on Saturday night about the impending disclosure of his affair in the News of the World.
Mr Major was informed of the allegations on Saturday, before returning from a holiday in France. Full details were on his desk by the time he reached Downing Street. In a clear sign of his displeasure the customary exchange of letters on a ministerial resignation did not take place as it was considered "unnecessary".
"People who accept high office, a minister of the Crown, wear an England shirt," said David Evans, a member of the executive of the Tory backbench 1922 Committee and a former parliamentary private secretary at the Welsh Office. "You have to set an example. There are standards to be set and if a minister of the Crown misbehaves in this way, that's it. No problem," Mr Evans told BBC Radio 4's The World This Weekend programme.
Mr Richards refused to comment as he and his sons left the family home at Colwyn Bay, in his Clwyd North West constituency, yesterday.
Mr Richards may also face deselection by his constituency. But, even if that were to happen, a subsequent by-election is considered unlikely.
A junior minister in the Welsh Office since 1994, Mr Richards is a fluent Welsh speaker and former BBC broadcaster.
He was forced to apologise after describing Labour local councillors in Wales as "short, fat, slimy and corrupt".Reuse content