Worcestershire are closing in on a third successive victory in the Specsavers County Championship after an outstanding third day with bat and ball in the home clash with Leicestershire.
The County extended their overnight total from 270-4 to 493 all out thanks to fine contributions from Ben Cox, Ravichandran Ashwin, Ed Barnard and Leach to secure maximum batting points.
Then Leach and Josh Tongue got to work with the new ball in dramatic fashion in reducing Leicestershire to 10-4.
Tongue struck with his first ball of the innings as Ned Eckersley (0) went for a pull and bottom edged a low catch to Cox.
Then with the last ball of the over Colin Ackerman (4) nicked a ball that moved away through to Cox.
Leach then got in on the wicket-taking act as Leicestershire skipper Mark Cosgrove (0) was trapped lbw and Michael Carberry (1) was bowled after offering no shot.
First innings century-maker Neil Dexter and Aadil Ali added 49 in 18 overs for the fifth wicket.
But then the wickets started to tumble again after Barnard trapped Ali (24) leg before.
Ashwin settled into a good groove at the New Road End and was rewarded with two late wickets.
Dexter (48) went lbw and in the last over Ben Raine (10) was caught at second slip to round off a highly satisfactory day.
Worcestershire secured maximum batting points despite a career best performance from Leicestershire spinner Callum Parkinson of 8-148 from 45 overs.
Nightwatchman Tongue (10) was neatly stumped by Lewis Hill off Parkinson.
Brett D’Oliveira added 17 to his overnight 121 not out before he was caught and bowled off a leading edge by Parkinson.
His splendid 207 ball knock contained one six and 15 fours.
Ashwin and Cox then accelerated Worcestershire towards maximum batting points with a stand of 67 in 10 overs.
Ashwin reeled off a series of impressive drives in making 44 off just 50 balls with six boundaries.
But Parkinson returned to the attack after an initial flurry with the seamers via the second new ball and enjoyed a sixth success.
Ashwin drove at the 20-year-old and Ned Eckerlsey held onto a fine low chance at cover.
Cox had an escape on nine when Ecklersley spilled the chance at second slip off Dieter Klein but then flourished.
New batsman Ed Barnard also survived a stumping opportunity to Hill off Parkinson on 20.
Cox completed his fifty – from 68 balls with five fours and a six – in the final over before lunch with a lofted straight drive for four off Parkinson and also brought up the half century stand with Barnard (26 not out).
The stand was extended to 63 in 17 overs before Barnard, who passes 500 Championship runs for the season, played back to Ben Raine and was caught behind for 30.
Leach struck a robust 28 before providing a return catch to Parkinson who ended the innings when Cox (77) was caught at mid off.
The wicket-keeper batsman hit one six and six fours in his 107 ball knock.