Richards played for England in last year's November internationals

The 29-year-old, who has six England caps, started his professional career with the Exiles in 1997.

"I'm really looking forward to returning. I started my senior career there and it has always had fond memories for me," said Richards.

Richards has also had spells with Harlequins, Bristol and Wasps.

He added: "I realise that things have changed dramatically at the club, not least the style of play and the depth of talent in the squad.

"I want to play a full part in the club's progress and in doing so I hope to give my England prospects a boost."

Peter has a proven track record London Irish director of rugby Brian Smith

Richards has played for England at every level from Under 16 upwards, as well as featuring for his country on the Sevens circuit.

"Peter is an important signing for us," said London Irish director of rugby Brian Smith.

"With up to 35 top-class games to play each season we need two scrum-halves of real, international calibre if we are to be competitive.

"It is asking a lot of one player to play to a high standard in so many games. We want to be in a position where all our backs are capable of scoring tries.

"Peter has a proven track record in that regard and we're looking forward to having him back at Sunbury."

Last week, Gloucester completed the signing of former Munster scrum-half Mike Prendergast on a two-year deal.