England all-rounder Jamie Dalrymple has rejected a new Middlesex contract to join Glamorgan on a three-year deal.
Dalrymple playing for Middlesex in the 2007 Twenty20 Cup
Dalrymple, 26, played in 27 one-day internationals including the Commonwealth Bank Series triumph in Australia and the 2007 World Cup.
But he had a poor summer at Middlesex and has sought a fresh start.
Glamorgan cricket manager Matthew Maynard said: "I'm absolutely thrilled that such a proven quality cricketer as Jamie has joined Glamorgan."
Born in Kenya, Dalrymple went to Radley, the same school as Andrew Strauss, and later skippered Oxford University.
But the off-spinner and lower middle order batsman was a surprise selection in Duncan Fletcher's one-day squad to play Sri Lanka in the summer of 2006.
Some initial success for England tailed off later on, however, and he has not attracted the attention of Fletcher's successor Peter Moores.
Dalrymple said: "I have had a wonderful time at Middlesex and have many friends there on and off the field.
"It has been one of the most difficult decisions of my life but the time was right to seek a fresh challenge and a new opportunity."
Middlesex chief executive Vinny Codrington said: "JD has been a large part of the family and we are really sorry to lose him."
Maynard added: "This sends out a great message to everyone about the direction in which the club is heading.
"Jamie offers great strength and international experience to our squad, and I have no doubt whatsoever that he will be able to contribute to all departments in both our one-day and four-day teams."
"I thoroughly enjoyed working with Jamie when I was part of the England coaching set-up, especially during the World Cup in the Caribbean.
"Jamie has got a great attitude and he has the right character to fit into the Glamorgan dressing room."
"I know that his ability and character are exactly what this squad is looking for, so for me it was really important to persuade Jamie to come to Wales and join Glamorgan."
Seam bowler Chad Keegan has also left Middlesex after the club decided not to offer him a new contract.
"Chad's injury problems have curtailed his playing career and we are terribly sorry to see him leave us after seven years, in which he has had a huge influence on the club, both on and off the field," said director of cricket John Emburey.