Trinity, having conceded the same number of goals on their two previous visits, only competed after defender Tom Davie was sent off for a poor tackle on Ryan Jennings in the 26th minute.
Boss John McDermott described his side’s performance in the 4-1 win as “fantastic for the first 45.”
“l thought we were electric to be honest and we would beat anyone in our league. Everyone was on it, from one to 11.
“They were on the top of their game, moved and passed it well and looked a threat every time we went forward.
“We totally bossed it and l think 4-0 probably flattered them. We could have got a few more.
“l was really pleased with it — everyone did their job, from the back to the front.
“We moved the ball really well and there were good little interchanges with certain players. It was breath-taking at times.
“l said to the lads that’s how we want them to play, that’s how we’re going to play — it’s been in them from the minute we walked through the gates the first day we came in.
“One or two have been added to the squad and have just brought that little bit of cleverness, sharpness, brightness, bravery to try and take a chance in the final third and create.”
Tom Platt, who had won the previous game for the Reds at Leamington with a last-gasp goal, opened the floodgates in the eighth minute when he guided Brendon Daniels’ cross over the line from close range, after Ricky German had linked with Craig Westcarr.
Four minutes later Westcarr was in the right place to divert a Daniels free-kick past visiting keeper Henrich Ravas.
Five minutes later another Daniels free-kick picked out German, the young on-loan striker from Chesterfield FC making his first start for the Reds, who swivelled to plant the ball neatly past Ravas.
The Reds’ scoring was completed when Daniels fittingly scored direct from another free-kick to round off a superb personal performance.
Seconds later Davie received his marching orders and the dynamic of the game changed with Alfreton no longer able to carve their way through with the ease, despite the man advantage.
McDermott added: “l wanted them to keep pressing and give them a real good hiding.
“l’ve been in games where it doesn’t happen, they get men behind the ball, make it difficult for you and we just didn’t move it as quick as in the first half.
“We didn’t take enough chances. As l see it they’ve got ten men and they’ve scored, so they’ve beaten us 1-0 that half — we have to work on that.”
Gainsborough undoubtedly deserved their consolation goal, which was only the second conceded at home by the Reds in five games this season, as Bradley Wells followed up after Chris Elliott had parried an angled drive from John Evans.
ALFRETON: Elliott; Wood, Shiels, Priestley, Keane, Jennings, Platt [Topliss 54], Disley, Daniels, Westcarr [Robertson 71], German [Sharp 71].
Other subs: Allan, Smith.
GAINSBOROUGH: Ravas; Jacklin, Davie, Clarke, Stainfield, Evans, Wells, Collins [Storey 26], Richards [Gater 63], Worsfold [Wafula 74], King.
Other subs: Lacey, Jones.
Referee: David McNamara.