The Combined Counties took their first step towards Twickenham with a committed display.
Bucks took an early lead with a penalty from full back John Smith, but in the 17th minute Wimborne lock Leyland drove over the home line to open the Dorset and Wilts account with a try. Glamorgan Wanders full back Mark Haywood converted.
The Twin Counties won possession from a line out close to the Bucks line and a set play put Tinsdale in the clear to touchdown in the corner .
Following the restart a Counties player was caught fringing and Smith stepped up to punish the visitors with his second penalty goal.
Salisbury fly half John Penry then worked the ball back inside for James Gaiger to claim the touchdown.
Eighteen minutes of the second half had elapsed when Wootton Bassett full back David Parker took possession inside his own in goal, he elected to run with ball in hand and broke free.
The ball travelled between six pairs of hands before finding its way back to Parker and he sprinted in beneath the Bucks posts. Haywood converted.
Replacement scrum half Tom Collins scored another touchdown and Haywood again converted. A minute into overtime Andy Gould touched down in the corner for the final score. Haywood converted .
On Saturday Dorset and Wilts must beat Oxfordshire at Swanage and Wareham's Bestwall Park if they are to progress.
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