Mark Stoneman is to leave Surrey and join Middlesex on a three-year deal.
Stoneman, the former England Test opener, had been offered a new deal to remain at The Kia Oval but has been lured to Lord's by a long-term contract and the prospect featuring in all three formats of the county game. Stoneman has struggled to gain a place in Surrey's T20 team.
The 34-year-old, who has spent five years at Surrey having previously represented Durham, is to join Middlesex on loan immediately and is available for their final four LV= Insurance County Championship matches of the season. The deal secures his future at Middlesex until at least the end of 2024.
"Mark brings a wealth of experience from the cricket side of things, and it will be great to use that experience to drive our young batsmen forward," Stuart Law, the Middlesex head coach, said. "[He is] a tough no-nonsense bloke who will form an experienced opening partnership with Sam Robson at the top of the order.
"This is a significant signing for us as we build a squad for future success here at Middlesex, and it won't be the last signing we make before next season. There'll be more to come on this in the coming weeks."
Stoneman started and finished his Surrey career with centuries. After making 165 in his first Championship innings for the club (against Warwickshire) in 2017, he finished with a List A century against Glamorgan on Tuesday in the Royal London One-day Cup semi-final. In between times, he won 11 Test caps and played an important role in Surrey's Championship-winning side of 2018.
"I have had a fantastic five years at Surrey and will be forever grateful to Alec Stewart for giving me the opportunity to represent the club," Stoneman said. "They played a key part in helping me achieve an ambition of playing for England. It was an incredibly difficult decision to turn down their contract offer as I've loved being part of the Surrey family.
"During my time at the club, I have received fantastic support both on and off the field. However, I was offered a fantastic opportunity by Middlesex and I'm grateful to Alec for his understanding of my decision."
Stewart, Surrey's director of cricket, admitted he was disappointed to lose Stoneman, but wished him well.
"We are obviously disappointed that Rocky chose not to accept our new contract, but I respect his decision and the reasoning behind his move," Stewart said. "He has been brilliant to work with during his time at Surrey and I wish him every success as he joins Middlesex."