Middlesex 347 for 6 dec and 184 for 3 (Gubbins 49*) lead Surrey 282 (Borthwick 92, Smith 80, Stoneman 45, Murtagh 5-47) by 249 runs
Tim Murtagh's devastating second-new-ball spell of 6-5-4-4, and a dramatic Surrey collapse in which they lost their last seven first innings wickets for only 28 runs in 15 overs either side of lunch, has given Middlesex full control of the Bob Willis Trophy's London derby.
By the end of day three Middlesex had stretched their overall lead to 249 by reaching 184 for 3 in their second innings with Max Holden scoring 43 and Nick Gubbins following up his first innings 192 with 49 not out. Gubbins added a handy 71 in just 11 overs in the late afternoon sunshine with Martin Andersson, who has so far hit seven fours in a punchy unbeaten 35 off 37 balls.
Holden was joined by Sam Robson in a first wicket stand of 70 before being brilliantly caught by Rikki Clarke at slip off slow left-armer Dan Moriarty, who then had Robson caught behind from one that bounced and turned and Stephen Eskinazi taken at short leg for 18 in a fine spell of 3 for 39 from 15 accurate overs.
Veteran seamer Murtagh, who turned 39 on day two of this match, earlier finished with figures of 5 for 47 as Surrey, at one stage cruising on 254 for 3 in reply to Middlesex's 347 for 6 declared, were tumbled out for 282. And, despite the efforts of Moriarity, 20, on his first-class debut, Middlesex will fancy their chances of beating their traditional rivals on a pitch that is starting to take more spin and also showing some signs of inconsistent bounce.
Most counties are facing this abbreviated season with significant absentees, particularly those who are included in the extended England Test and one-day international 'bubbles', but Surrey are perhaps more handicapped than others in the South Group with a full XI of senior players currently unavailable.
This includes their seven England squad players, two Kolpak-registered South Africans Morne Morkel and Hashim Amla, absent due to global travel restrictions, and the pace bowlers Liam Plunkett, Conor McKerr and Jade Dernbach because of injury niggles.
And Middlesex, although themselves without the powerful fast bowling trio of Steven Finn, Toby Roland-Jones and Tom Helm, still have the estimable Murtagh to lead their attack and he swept aside Jordan Clark, Moriarty, Matt Dunn and Amar Virdi to take his career first-class wickets tally to 821.
The third day, however, had begun with Surrey looking the likeliest side to get on top until Scott Borthwick's dismissal for 92, hoicking a first-ball long hop from Andersson to midwicket, and which followed a fourth wicket stand of 105 with Jamie Smith, who went on to make an impressive 80 from 166 balls, with a six and 14 fours.
Surrey had resumed on 189 for 3, and initially Borthwick and Smith added a further 65 in 18 overs. But, just when it seemed that Surrey would push on to a first-innings advantage for themselves, Borthwick fell in the 86th over - after facing 240 balls, hitting 12 fours - and, suddenly, fortunes changed.
Clarke was well caught by wicketkeeper John Simpson for 1, gloving a sweep at legspinner Nathan Sowter, and then Murtagh grabbed the second new ball to huge effect. Clark and Moriarty fell before lunch, and Dunn and Virdi to consecutive balls to finish off the innings soon after Smith was eighth out, caught at second slip off Miguel Cummins.
Clark was superbly held by a diving Simpson for 1, trying to leg glance, and Moriarty leg-before for a duck. Dunn was bowled for 1 by a beauty which clipped the top of his off stump and Virdi was struck in front shuffling across to his first ball. No fewer than 13 of Murtagh's 27 overs were maidens.