A stunning 11th-minute strike from Adam Randell set Bristol City on course for a thumping 5-0 New Year's Day victory over Portsmouth at Ashton Gate.
The former Plymouth midfielder shocked the massed ranks of Pompey fans behind the goal with the sweetest of right-footed shots into the top corner from 25 yards after a cross into the area had been cleared into his path.
The quality of that effort was almost matched by Anis Mehmeti after 24 minutes, his precise strike from outside the area skidding low past Portsmouth goalkeeper Nicolas Schmid following a defensive mix-up.
It was 3-0 five minutes after the break thanks to Scott Twine's first-time, left-footed shot from 10 yards from a Neto Borges cross.
More calamitous defending saw Sinclair Armstrong slot the fourth from close range nine minutes later after fellow substitute Sam Bell had won possession on the right of the box.
An unstoppable Armstrong drive, rifled home in stoppage time, completed the rout as the impressive Robins kept in close touch with the Championship play-off places, while Pompey were left to lick their wounds.
City played in white and black, rather than their traditional red and white, as a tribute to the team which clinched promotion to the top flight with victory over Portsmouth at Ashton Gate 50 seasons ago and wore the strip for away games in the old First Division. Many of those players were introduced to the crowd before kick-off, along with manager Alan Dicks, now aged 91.
They saw their old club dominate the first half, allowing Portsmouth just one clear sight of goal. That came after 19 minutes when Ibane Bowat headed just over from a John Swift free-kick on the left.
City were by far the more threatening. After two quality goals had put them in command, Mehmeti was twice denied by Schmid saves, the second diving to his right after Conor Shaughnessy's wayward pass had put Pompey in trouble.
Twine volleyed narrowly wide in first-half stoppage time and there were jeers from Portsmouth's large contingent of travelling fans at the half-time whistle, having seen their side make sloppy defensive errors.
That continued at the start of the second half when another mix-up resulted in Emil Riis having a shot deflected wide.
After Twine's goal, City head coach Gerhard Struber sent on Yu Hirakawa, Armstrong and Bell, returning after a lengthy injury absence to claim an assist for the fourth.
Pompey boss John Mousinho also made full use of his bench with five second-half changes but could do nothing to lift a nightmare performance as Armstrong squandered two great chances to extend City's lead before his emphatic late finish.
The managers
Bristol City's Gerhard Struber:
To follow...
Portsmouth's John Mousinho:
To follow...