Ollie Rayner's career-best return accelerated Middlesex towards a victory over Surrey at the Kia Oval which would push their London rivals deeper into the LV= County Championship Division One relegation mire.
The off-spinner sliced Surrey in a remarkable afternoon session to record figures of 8-46 as the hosts were reduced to 145 all out before tea, having been 59 for one at lunch.
By the close, Surrey were 282 runs adrift as the visitors reached 133 for five in their second innings, with Dawid Malan finishing unbeaten on 28, but the day belonged to Rayner.
The 27-year-old used his height well to get extra bounce from a dusty surface, as well as being able to push the ball through and deny Surrey's batsmen the chance to get down the pitch to him.
Surrey had begun the day well by picking up the last three Middlesex first-innings wickets for just 14 runs after resuming on 280 for seven.
Jade Dernbach had James Harris leg before with the second ball of the day and Ravi Patel was held at first slip off Stuart Meaker for one.
Neil Dexter, on 77 overnight, tried to hit out in a bid to gain a third batting point, but was left stranded on 90 not out when last man Corey Collymore was out in bizarre fashion as he ducked a slower ball from Dernbach only for it to loop over him and clatter into the leg stump on the full.
Surrey lost Arun Harinath to the second over of the day yet Rory Burns and Hashim Amla seemed to steady the innings with a partnership of 70.
The final ball of the fourth over after lunch, however, was a low full toss from slow left-arm spinner Patel which South African Test star Amla hit straight to Rayner at mid-on.
Rayner then struck three times in quick succession to remove Burns, Zander de Bruyn and Steven Davies, before Vikram Solanki skipped down the pitch on 24 and drove the tweaker to Dexter at short midwicket.
Meaker became Rayner’s fifth victim and he then cleaned up the tail with the added scalps of Tim Linley, Gareth Batty and Dernbach.
Surrey had lost nine wickets inside 33 overs and not even a five-for from Gary Keedy after tea could prevent Middlesex from moving into a seemingly impregnable position by stumps.
Keedy had Sam Robson, Dexter and Gareth Berg caught by Solanki in the gully while Chris Rogers went for 32 and John Simpson for 12.
Malan, however, kept up the attacking approach while Harris came in as a nightwatchman ahead of Rayner and migraine victim Joe Denly to keep him company until the close.