Left-arm seamer Tomlinson took the first six Somerset wickets at a cost of just 12 runs in 4.2 overs to leave the home side in tatters at 23 for six before Craig Kieswetter (32) and Ben Phillips (39) helped them to 126 all out.

In reply, Hampshire were struggling at three for two before Pietersen (100) joined John Crawley (78 not out) in a third wicket stand of 190. They closed on 194 for three, with a lead of 68.

Tomlinson went into the game with only 49 first-class wickets in a career which began in 2002.

The former Cardiff University bowler has struggled with injuries, but relished the chance to perform on a damp pitch.

In his second over he struck with his second, third and fifth deliveries to remove Neil Edwards, bowled for five, Justin Langer and James Hildreth.

Langer fell for a first ball duck, loosely cutting a wide ball to backward point where Sean Ervine took a smart diving catch. Hildreth was snapped up at short-leg and Somerset had plunged to 11 for three.

Worse was to follow for the top-flight newcomers as Marcus Trescothick was caught in the slips for 11, Zander de Bruyn suffered a similar fate and Peter Trego was lbw first ball.

Tomlinson was swinging the ball in and getting some seam movement – but was aided by some poor shot selection from the Somerset batsmen.

Ian Blackwell (17) helped Kieswetter take the score to 55 before becoming a first Championship victim for 18-year-old seamer Hamza Riazuddin, who bowled tidily on debut to take one for 21 from six overs.

Phillips and Kieswetter added 50 for the eighth wicket before Tomlinson struck again, removing the latter's off-stump with a ball which held its line.

Michael Munday fell to David Griffiths and Phillips was last man out – having hit seven fours before being caught at slip – to complete Tomlinson's figures of 14.2-2-46-8.

The wickets continued to tumble as Hampshire openers Michael Brown and Jimmy Adams fell to Charl Willoughby and Phillips respectively.

But Pietersen came in to produce the first really authoritative batting of the match.