Johnson played three Tests and 10 ODIs for England in 2003

The 31-year-old has agreed a two-year contract only days after telling a newspaper he wanted to stay at Taunton.

"I've had a fantastic six years, I was offered a new deal but it just didn't quite add up," he told BBC Sport.

"I felt I might be a bit part player at Somerset, who have made a few signings, Middlesex desperately wanted me back and I think it's a fantastic move."

Johnson, who had also attracted interest from Kent, has more than 520 first-class wickets to his credit.

He first hit the headlines in 1994 by taking all 10 wickets in an innings for Middlesex against Derbyshire and was picked to tour South Africa with England the following year, only to pull out because of back problems.

His move to Somerset occurred in 2001 and he helped them win the C&G Trophy and finish runners-up in the Championship in his debut season.

He was rewarded with a place in the England squad for the trip to India that winter, but had to wait until 2003 to finally make his Test debut against Zimbabwe at Chester-le-Street, an occasion he marked with figures of 6-33 in their first innings.

Johnson played three Tests that year but his hopes of adding further caps have been hampered by a series of injuries and he only played half of Somerset's Championship matches during the 2006 season.

He is Middlesex's third signing of the winter following the arrival of Sri Lanka Test star Chaminda Vaas and Indian spinner Murali Kartik.

Johnson is enthused by the prospect of partnering Vaas, and said of the Sri Lankan: "He's a brilliant bowler and I hope to pick up a few pointers

"I'll be 32 next month and to go back and play for Middlesex for the last couple of years is fantastic," said Johnson, who spent eight years with the county.

"I managed to get into three finals at Somerset and won two but never won anything at Middlesex."

The fact that Middlesex finished bottom of both the Championship and Pro40 does not deter the seamer.

"They've been a strong side, they had a hiccup last season, they lost Jamie Dalrymple and Ed Joyce for a while but there is a lot of young talent coming through, mixed with experience, and they're a useful side, they want to get promoted straightaway and hopefully I'll be there to help them do that."

Middlesex chief executive Vinny Codrington said: "We are delighted Richard Johnson is coming back to join us.

"We would like to thank Somerset for the most amicable and professional way in which these negotiations have been carried out."

Meanwhile, South African-born paceman Chad Keegan, who took 19 wickets in seven Championship matches last term, has agreed to stay with the county for the 2007 season.