It was a first trip to a damp Dublin for many of Lancaster's new-look side and they faced an Irish team not only with more than twice as many caps, but also momentum of their own following impressive back-to-back wins over Argentina and Wales.
That impetus was quickly ended thanks to a string of first- half errors and a high-pressure game from an English team for whom young flyhalf Owen Farrell clinically took his chances in a well deserved 12-6 win.
"To come here with a young side and show that kind of maturity to close the game out was hugely pleasing," Lancaster, who has transformed England into a far more disciplined unit since taking charge over a year ago, told a news conference.
"It was composure in the heat of the battle. It's a very difficult place to come and play rugby. To play against a side as good as Ireland with so many experience players when we've got lads in single-figure caps, it's a great testament to their maturity."
The victory means England are the only unbeaten team in the competition after just two rounds and the only one capable of winning the grand slam, a feat they last accomplished 10 years ago under the captaincy of Lancaster's predecessor Martin Johnson.
Graham Rowntee, another member of that 2003 squad and now England forwards' coach, said winning away from home proved the young side had backed up their stunning November victory over world champions New Zealand.
Attacking coach Mike Catt, a World Cup winner in 2003, was similarly impressed, and rounding off the top table of trainers, backs coach Andy Farrell saved his praise for the composure shown when Ireland levelled the scores just after the hour.
Flanker James Haskell had also just been sin-binned but England doubled their lead when down to 14 men with flyhalf Farrell, son of the rugby league great, pulling the strings to ensure a third successive win over the Irish.
"There was a tricky point in the third quarter where we had a couple of back-to-back errors but the way that we composed ourselves and finished the games stronger was a masterclass really of how to handle that last 20 minutes," Farrell senior said.
"For a young side to play like that in a pressured situation against a team that's been there and done that many times and been successful with it is a credit to everyone."