Andy Farrell believes Ireland have achieved their biggest feat yet by winning a series in New Zealand, a result that he suggests "won't be done again".

The tourists were humbled by the All Blacks in the first of three Tests but responded in sensational fashion with back-to-back victories – their first ever away wins in New Zealand.

A first such series success was secured on Saturday by a 32-22 win in which Ireland dominated the first half and dug in for the second.

And the long-awaited accomplishment is not one Farrell foresees happening again in a hurry.

"This is a special group, you know? To come over here and achieve what they've achieved, it won't be done again," the Ireland coach told Sky Sports. "Knowing what we know, that's not going to happen in the next few years, anyway.

"This is probably the toughest thing to do in world rugby.

"We came over here with task in hand, and we went for it straight from the start, which is great. It's a group of 40 players and a lot of staff, as well.

"We said it was going to be the start of our World Cup year, but I don't know... I think it is probably a little bit bigger than that."

Ireland led by 19 points at half-time, the biggest advantage against New Zealand at that stage of a match in Test history.

Having beaten one of the world's best sides, Farrell's men are confident they can take on any opponents.

"They already do believe that," he said. "They keep turning up and surprising me, certainly. The bunch are just tight, and they really do believe, they really do believe that.

"After the first game, we got held up over the try line five times and made plenty of opportunities in the second game, and they knew there was a better performance in them.

"There certainly was for that first 40, wasn't there? These guys have won a lot of stuff and broke some records – this one will top it, I would have thought."