Middlesex captain Shaun Udal was knocked unconscious after being struck on the head during a frenetic second day against Northamptonshire.

In only the fifth over of the day, 40-year-old Udal – who has appeared in four Tests and 11 one-day internationals for England – was caught on the back of the head as he attempted to duck a delivery from Johan van der Wath.

Play was delayed for nearly half an hour as Udal lay on the Wantage Road wicket before he inevitably retired hurt.

John Simpson regrouped for the visitors as he hit 87 in his maiden first-class innings but wickets fell throughout the day in the LV= County Championship Division Two match.

Middlesex finished the day at with a lead of just 29, with seven second-innings wickets standing, after bowling out Northamptonshire and then losing three batsmen cheaply before the close.

Middlesex finished with a first-innings total of 259, and Gareth Berg then took five wickets as Northamptonshire were bowled out for 239 inside a session and a half.

Resuming this morning on 206 for six, Middlesex lost the injured Udal and Murali Kartik (7) soon followed as he hit a delivery from Van der Wath straight to David Lucas at cover.

Tim Murtagh (2) was the next to go when he was caught at second slip by Riki Wessels off the bowling of Lee Daggett.

Simpson was the last man out when he was bowled by Daggett with the last ball before lunch, having scored a classy 87 off 141 balls including 11 fours and one six.

Northamptonshire’s reply got off to a terrible start when they lost Stephen Peters and Niall O’Brien in the first four overs.

Peters edged to Nick Compton off Murtagh for a duck before O’Brien flashed a poor shot from a Steven Finn delivery straight to Dawid Malan at slip.

Worse was to follow as Finn claimed his 50th wicket of the season when Wessels was well caught by Compton before Alex Wakely (9) also fell by the wayside when Murtagh took out his off stump to leave Northants on 40 for four.

Rob White led the resistance for the home side, making 47 from 48 balls before he misjudged a ball by Berg and was bowled.

Andrew Hall made 38, but he went for one shot too many and skied Finn to Dan Housego near the boundary just before tea.

Van der Wath was the next to go when he was clean bowled for 38 by Berg, who proceeded to claim the remaining wickets of Nicky Boje (51), Monty Panesar (7) and Daggett (1).

Middlesex’s attempt to see out the remaining 11 overs as cautiously as possible backfired spectacularly as two rising deliveries from Lucas accounted for Compton and Housego.

Night-watchman Finn also departed for a duck when he was bowled by Van der Wath, leaving Middlesex 17 for three.