The Compton skipper walked to the crease with his side rocking at 19-3 in a Hampshire League Division 5 South East match against Railway Triangle 2nds.
Incredibly, he was seventh out with the Compton score on 304 – after blitzing 214 off just 100 deliveries!
Turner, whose previous best league score was 95 six years ago, cleared the boundary rope 10 times and also hit 24 fours in a glorious innings.
Triangle skipper Stuart White (4-40, including the first three wickets to fall) tried nine different bowlers in a bid to dismiss Turner - Neil Jones eventually trapping him leg before.
Alex Elms was Compton’s next highest scorer with just 21 - 193 runs fewer than his skipper managed.
Turner and Elms put on 82 for the fourth wicket before Turner dominated a stand of 132 for the fifth wicket with Andrew Jones (17).
Thanks to Turner’s double ton, Compton closed on 336-9 in 40 overs.
In reply, and no doubt still shell-shocked, the hosts were dismissed for 113 to lose by a mammoth 223 runs.
Opener Ben Jones (57) was one of only two players to reach double figures - No 9 Zoe Stride (11 not out) was the other - before he was run out by Turner.
Henry Slatter (3-34) had taken out the top of the Triangle order, and Liam Dawtry (4-17) mopped up the tail.