Sir Clive Woodward's men scored 17 tries in total and were 38-6 ahead at the interval as Williams completed his hat-trick and Martin Corry, Jason Robinson and Geordan Murphy all helped themselves.
Manawatu were a broken side long before half-time and when the Lions re-emerged they continued the scoring spree. Charlie Hodgson, Ollie Smith, Neil Back, Gordon D'Arcy, Gareth Cooper, Ronan O'Gara (twice) and Mark Cueto (twice) gorged themselves on a feast of attacking ball.
Williams, who had started the rout, fittingly brought up the century of points with his fifth try five minutes from time.
Manawatu are regarded as the weakest opposition the Lions will face and with the All Blacks awaiting in the second Test on Saturday, the execution needed to be clinical.
It was. The handling was precise, the line-out functioned well and - in the opening half hour when the game was still a contest - the Lions looked like a serious, consistent attacking threat.
It took only three minutes for them to fashion the opening. Quick hands from Murphy set Robinson free and when he was hauled down the Lions transferred the ball out to the opposite winger where Williams beat his man brilliantly to score.
Andrew Sheridan peeled off the back of a ruck, fed Robinson down the short side and quick passing via Cusiter opened the space for Corry to charge over the line.
Hodgson, on pure form, made a case to be the Lions Test fly-half. His tactical kicking game was superb and he brought calm authority to the Lions.
The tries continued to flow. After Cusiter had taken a quick tap, Williams brushed off a heavy tackle from Manawatu hooker Nathan Kemp, spun free and darted to the line for his second of the game.
The Lions continued to run at Manawatu and Murphy stepped inside off the right wing to glide past two stranded defenders and open the Lions a 26-0 lead just before the half hour.
Manawatu's back had been broken. Kemp was sin-binned for a high tackle on Hodgson and immediately the New Zealanders were made to pay as Robinson scooted down the right wing to score his first try in any rugby since January 2.
Jonathan Hargreaves landed two penalties but in between those kicks Williams completed his hat-trick after Ollie Smith had off-loaded brilliantly out of the tackle.
The Lions made a number of changes at the interval. Brent Cockbain, called up as a replacement for Danny Grewcock, made his Lions debut for Donncha O'Callaghan while scrum-half Gareth Cooper and Back joined the fray.
Smith sparked an immediate attack and Hodgson capped an impressive all-round performance of 19 points with a neatly-taken try.
After setting up two scores, Smith brought up the half-century off a Cockbain pass and then Williams nailed his fourth on the opposite wing.
The Lions ploughed forward immediately from the restart as Simon Shaw charged 55 metres and set the platform for Back to dive over.
There was very little opposition now and the Lions moved 95-6 ahead as O'Gara, on for Hodgson, bagged a pair, as D'Arcy, Cueto and Cooper all got in on the action.
Matt Stevens was sin-binned for a professional foul but Williams then brought up the century of points before Cueto rounded off the night with the final move of the game.