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.
Bristol City's Gerhard Struber:
"It was the perfect start to the new year. I believed we had a result like that coming because we have been playing well without always scoring the goals we should have.
"Today our finishing was knife sharp. We could have had more goals and we never gave Portsmouth the slightest opportunity to get into the game, so I am super happy with the performance.
"Our pressing was synchronised and the energy level of the team was amazing. Now we have to seek the consistency to produce that type of display every week.
"I am hopeful of bringing players in during the transfer window, but it is not all about that. We also have to integrate any newcomers into our squad and ensure they share in the way we want to play.
"For the moment, I am delighted with the way the squad is developing and how well the current players are doing."
Portsmouth's John Mousinho:
"There were mitigating circumstances in terms of the injuries we have been carrying. It was a game too far for us in that respect and nothing has gone right on the day.
"The other night we patched things together and produced a result on the back of some other positive performances, but today was just too much.
"The players know that display wasn't good enough and so do the coaching staff. But it wasn't a time for throwing tea cups after the game because the lads have been working hard and doing their best.
"The first goal was a brilliant strike and there was little we could do about it. But I was disappointed by the way it deflated us."
