The opener took his 2022 league tally to 484 - easily the highest in the division - with 59 not out in a seven-wicket victory over Mudeford.
It was the fourth time he had passed 50 in HL action this season, but the first in which he hadn’t reached three figures.
He was prevented from doing so for a fourth time by the fact Mudeford had been bowled out for 152 after winning the toss.
George McDowell (3-23) was the leading wicket-taker for Locks, with No 7 Rich Wakelin’s unbeaten 45 the hosts’ top score.
After taking a single off the first ball of the Locks reply, Baker then saw opening partner Matt Wake trapped leg before from the second.
But Andrew Booth (29) and Jon Whitfield (34) helped overcome that early shock.
Joe Acaster (21 not out) then came in at No 5 to finish the game off with two sixes and two fours in the 23rd over.
Baker had started the day in second place in the overall Hampshire League run charts, behind Petersfield’s Henry Shore.
But while Shore followed a run of three successive centuries with a duck, Baker did not take over top spot.
Instead, Wickham’s Peter Gwynn leapt from seventh place to first with a sparkling undefeated 155 for Wickham in a Division 5 South East fixture against Fareham & Crofton 3rds.
Locks, though, reduced Calmore’s lead to seven points, meaning the stage is set for a titanic battle between the top two at Locks this coming weekend. With both sides having won all seven games so far, something has to give.
Fareham & Crofton 2nds’ woes go on, suffering a sixth defeat in seven games - the other one was tied - against Ellingham at Bath Lane.
Sam Lindsay (37) top scored as the hosts were bowled out for 147 after being inserted. No 9 Nathan Lever and extras (both 24) were next highest.
F & C club chairman Charlie Stubbs dismissed Ellingham opener Charles Cockhram (2) cheaply. But skipper Mark Burrett (80 not out) and Nick Roe (39) added 118 for the second wicket as the hosts eventually nosedived to a seven-wicket loss.
In only his third innings for Sarisbury 2nds, Jack Robson reached three figures - hitting 101 in a thumping victory over New Milton 2nds.
The former Hook & Newnham batter, who has not played regularly for a few years, helped the visitors amass 310-6 after Simon Orr (61) and Will Bolton (45) had added 127 for the second wicket.
Robson scored three centuries for Hook, including a career high 116 in a friendly against Liphook in 2017. League wise, his best is 112 in the Hampshire League against Shrewton in 2016.
Chris Sanders then ran through the Milton to order to finish with 5-25, his second best league figures. Coincidentally, his best haul is the 6-25 he took for Sarisbury against Milton in a 1st XI fixture three years ago!
With No 10 Andrew Pritchett (32) and No 8 A Strawbridge (29) top scoring, Milton’s tag certainly wagged. But they were still dismissed for 156 to lose by 154 runs.