Surrey win third straight County Championship after Somerset defeat
The London-based county crushed Durham by 10 wickets at the Oval on Thursday - their sixth victory in seven home games in the first-class competition this season.
Somerset needed to beat relegation-threatened Lancashire on the fourth and final day of their match at Old Trafford to stay in the hunt for their first-ever Championship title.
But they slipped to a 168-run defeat and, with one game remaining, can no longer catch their rivals, whom they beat last week.
"To do it three times in a row is very satisfying," Surrey head coach Gareth Batty told the BBC.
"We shall enjoy today and then start the hard work tomorrow to do it all again.
"Every time you get over the line it's the hardest one because other teams are trying to close the gap, trying to improve their squads, improve their players.
"I feel like we are still keeping some distance, in a healthy, confident way, not in an arrogant way, because we're working incredibly hard trying to improve our performances year in and year out."
Surrey, who face Essex at Chelmsford in the final round of the Championship, have now won the competition 23 times, 10 fewer than record holders Yorkshire.