Match scores (The Oval)
Surrey won by seven wickets
Middlesex inns (50 overs): 243-9 (Simpson 75, Gubbins 65, Franklin 35; Rampaul 4-40)
Surrey inns (45.2 overs): 244-3 (Burns 67*, Sangakkara 59, Foakes 55*)
Match report
An unbroken fourth wicket stand of 117 runs in 19 overs between Rory Burns (67) and Ben Foakes (55) took Surrey to victory by seven wickets in their Royal London One-Day Cup match against Middlesex at the Oval.
Middlesex, with just one victory in four matches, are now facing an uphill struggle to progress after failing to defend a score of 243 for nine having been put into bat.
The visitors made the breakthrough they needed when Toby Roland-Jones bowled Mark Stoneman for 10 in the fifth over - but Surrey responded well.
Scott Borthwick flicked Tom Helm over square-leg for six and Kumar Sangakkara got into his stride when he hit Helm for successive fours, on-driving and then lofting over mid-on.
This pair put Surrey firmly in control with a second wicket partnership of 91. But Borthwick then chipped Dawid Malan to long-off and Sangakkara drove Malan straight to cover for a 68-ball 59 to leave the game in the balance at 127 for three. But then Burns and Foakes took charge.
When Middlesex batted they only looked capable of a formidable total when first Nick Gubbins and then John Simpson were at the wicket, but neither player survived to play the much needed major innings.
They were already depleted without their England and Ireland representatives, and then they decided to play Nick Compton ahead of the impressively in form Stevie Eskinazi.
Tom Curran broke through for Surrey with the last ball of the ninth over when Malan pulled to Stoneman at deep square-leg for just 14.
That brought Compton to the wicket but the former England batsman's innings lasted just five deliveries. He was caught behind nibbling outside his off stump, and that meant Middlesex were 42 for two after 10 overs.
Gubbins kept swashbuckling away at one end but at the other Adam Voges soon perished when he was caught down the leg-side for nine.
Gubbins looked well capable of making a century until he swiped Ravi Rampaul to Stuart Meaker for an 86-ball 65.
Simpson then took responsibility for the Middlesex innings. He was almost caught at long leg when he had made 51 but the missed half-chance didn't cost Surrey too dearly because he was lbw to Gareth Batty for 75, attempting to shovel the ball to leg.
Batty's ten overs cost just 38 runs, while Rampaul took four for 40.
After Gubbins and Simpson, the highest Middlesex scorer was James Franklin (35) and they needed 10 wides from the Surrey bowlers to get as many as they did.