Ireland coach Joe Schmidt says his side's "class and courage" helped them beat England at Twickenham to secure the third Grand Slam in their history.
Ireland, who had already sealed the Six Nations title, won 24-15 on Saturday.
"I thought our boys showed they can deliver in the big moments on a number of occasions. They worked incredibly hard and merited the win," he said.
"We showed a little bit of class where we opened them up and at the other end of the pitch it was pure courage."
Ireland's only previous Grand Slams came in 1948 and 2009 and their win in London was their 11th victory in succession, a national record and run of form which sees them move up to second in the IRB rankings behind world champions New Zealand.
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Tries from Garry Ringrose, CJ Stander and Jacob Stockdale, his seventh of the competition, helped the Irish to a 21-5 half-time lead, and a stubborn defensive display after the break helped see Schmidt's side over the line.
"I thought that some of the scores we put together were courageous, going up at the ball or chasing the ball," he said.
"We had to withstand about eight minutes of constant pressure inside our 22 at the start of the second half and we knew we couldn't afford to leak early points.
"Even at 21-5, we knew it would still be a real battle and to be fair to the players they delivered. It's fantastic for this group of players; they showed a fantastic mix of class and courage."
Ireland captain Rory Best added: "We knew it was going to be really tough but we tried to attack England from the start, with and without the ball.
"It was a ferocious Test match throughout but words can't describe how delighted we are with that win and with the Grand Slam.
"We set out to make every moment count and tried to build as perfect an 80 minutes as we could, hoping that effort would bring reward.
"I can't say enough about how everyone involved with the squad has gone about their business - we wanted to make a statement by winning something big and we have shown on the big stage what we are made of."
Greatest achievement in Irish rugby history - former players react
Former Ireland winger Denis Hickie on BBC Radio 5 live: "It's an incredible achievement for this team. Irish teams usually come to Twickenham with a lot of respect and a bit of fear.
"There are some world-class players in this Irish team - it's very fitting for them to win the Grand Slam.
"Joe Schmidt has taken this team to another level and they will always deliver. The challenge is can they keep it going and take it into next year's World Cup?"
Former Ireland winger Andrew Trimble on BBC Radio Ulster: "That was something special to witness, to see the guys accomplish what they have done at Twickenham.
"It's an amazing day that will live long in the memory. Joe Schmidt has accomplished something enormous in Irish rugby."
Ex-Ireland fly-half Tony Ward: "This is the greatest achievement in the history of Irish rugby. We have won all five games before but this time we beat the French in Paris and the English in London.
"Ireland were breathtaking in the first half and England threw everything at us in the second half but Ireland were relentless in their defence and thoroughly deserved to win."