Prospects appeared bleak for Hook when they slumped to 46-5 in response to a competitive Whitchurch total of 211-9 (Jack Dancer 78, Oli Webster 4-28).
But Manny, left, who plays for Hampshire Under-14s, belied his tender years and took up the challenge of turning the match on its head with an undefeated 115 off 102 balls.
Lumsden, whose father Audley was a prominent full-back for Bath and Gloucester in top English Premiership rugby, firstly shared an 83-run sixth-wicket stand with 12 years old, wicketkeeper Dan Corbett (17) to lift Hook’s reply to 129-6.
He then added another 69 with Charlie Bland (23), which took Hook to the brink of a remarkable win which retained the club’s Division 4 North status.
Hook & Newnham Basics are the second highest placed fourth team in the pyramid behind St Cross Symondians.