Celtic got the British record of 63 domestic games unbeaten that they were looking for, while St Johnstone’s run without a goal stretched on to six.
This was the result that most expected but the scoreline was a harsh on Saints, whose defensive shape was good for long spells of this contest.
Scott Sinclair, Moussa Dembele, Olivier Ntcham and a Steven Anderson own goal did the damage and laid bare the gap between Celtic and the rest.
Of the five injured St Johnstone players only Stefan Scougall was able to start, with Michael O’Halloran on the bench.
As at Celtic Park earlier in the season, Tommy Wright deployed two right-backs – Richard Foster and Aaron Comrie.
Saints coped well in the early stages, with a Moussa Dembele shot the closest Celtic came to scoring. It was saved comfortably by Zander Clark, though.
On 16 minutes a tidy exchange of first-time passes put Sinclair through but Clark read his intentions well and stuck out a foot to intercept as the winger attempted to round him.
There wasn’t much happening for Saints at the other end but Steven MacLean tried an ambitious lob from over 40 yards out and it drifted over.
Clark’s day was starting to get busier and he saved well from Sinclair low to his left.
Celtic took the lead just before the half-hour mark and they didn’t have to work too hard for it.
Stuart Armstrong’s corner was passed low to Sinclair, he lost his marker in the box, and gave Clark no chance with his finish.
Armstrong nearly doubled the visitors’ advantage a couple of minutes later when he curled a shot that Clark kept out at full stretch.
It was pretty much one-way traffic but during an increasingly rare spell of play at the Celtic end, Saints were awarded a free-kick 30 yards from goal.
Blair Alston had a go and it should have been a bread-and-butter save for Craig Gordon but the Scotland keeper nearly made a mess of a shot straight at him and only gathered at the second attempt.
Eight minutes after the re-start Celtic almost scored from another free-kick but Comrie headed Dedryck Boyata’s effort off the line.
Saints were feeding off scraps but when one fell into their lap they couldn’t make it count – a scuffed MacLean shot on 70 minutes.
To rub salt into the wound Celtic broke quickly up the pitch and Dembele finished off a flowing move from close-range to make it 2-0.
On 75 minutes it was three when Anderson put the ball into his own net from a Dembele cut-back.
With two minutes left a tired Saints conceded a fourth when Ntcham found the net with a low 18-yard drive.
