Over 300 representatives of the Irish community attended a reception in Buckingham Palace this evening.
The event was hosted by Britain's Queen Elizabeth and her husband, the Duke of Edinburgh.
The reception marked the contribution made by Irish people in Britain.
A spokesman from Buckingham Palace said: "It was a really fun evening - great company and extremely relaxed.
"Her Majesty seemed to enjoy the craic."
The event was held as preparations continue for the State visit of President Michael D Higgins and his wife, Sabina, to Britain next month.
It will be the first State visit to the UK undertaken by the president of Ireland.
Preparations for the visit have been going on for months.
Queen Elizabeth and the Duke hosted the reception for Irish people from different walks of life, including community activity, the arts, sport and culture.
One Direction's Niall Horan, singer Imelda May, impresario Louis Walsh, Irish designer Orla Kiely and Cork fishmonger Pat O’Connell, who charmed the Queen during her Irish visit, were among the guests.
The Queen asked Mr O’Connell if he had brought any fish with him.
Mr O'Connell recounted how he met the Queen at the English Market in Cork during her visit to Ireland in 2011.
Mr O'Connell made quite an impression during that visit, when he shared a joke with the Queen and the Duke of Edinburgh about an unattractive monkfish, which he said was nicknamed "the mother-in-law fish".
And at the Palace this evening, Mr O'Connell said he was "surprised" to be so swiftly recognised by the Queen, who he said greeted him by saying: "You're here, have you bought any fish with you?"
Mr O'Connell said: "We had great fun in Cork when she visited.
"I told the Queen when she last came to see me was the week of my 30th wedding anniversary and I said that the last time I was this well-dressed was 33 years ago."
"She laughed and then she asked me if I brought her any fish."
X-Factor judge Walsh said the Queen told him she would love to come back and visit the country.
"We talked about her visit to Ireland, she said she had a wonderful time and that she'd love to come back again.
"She said she thought she picked the perfect moment to come while Mary McAleese was still president.
"She is an amazing woman and she proved that on her visit. Everybody loves her.
"I didn't ask if she watches The X Factor but I think she might be watching Strictly Come Dancing."
The Queen and the Duke chatted with Irish guests from the world of sport, business, politics, the arts, and community work, who have all made a positive contribution to Britain.
Niall Horan described being at the Palace as "mind-blowing".
"It's an absolute honour to be here with two great countries coming together. I couldn't believe it when I got the invitation. To have met Her Majesty again was a great experience."
Horan, who had just come from rehearsing with his bandmates, said that they were pleased for him: "They were really happy when I told them. They know it's an Irish thing so they're not being left out."
"I might ask her if she wants to come to a show", he joked.
The Princess Royal, her husband Vice Admiral Sir Timothy Laurence, the Duke and Duchess of Gloucester, and the Duke of Kent were also at the Palace.
Irish ambassador to Britain Dan Mullhall and Northern Ireland Secretary of State Teresa Villiers also attended.
Mr Mulhall said there was "never a better time to be Irish in the UK".
"It is a wonderful occasion for the Irish community in Britain, the biggest Irish community anywhere in the world outside of Ireland," he said.
"They have made a huge contribution to Britain over the years, a huge contribution. Many of the people here tonight have been here for 40, 50 or even 60 years but they still have a proud Irish identity."
Ms Villiers said: "I think that the bilateral relationship is better than it has been at any time in the last 800 years.
"The President's visit is a wonderful opportunity for the Irish to celebrate the huge contribution they've made to life in Britain. This is a great curtain raiser to that."
A spokesman for Buckingham Palace commented on President Higgins' forthcoming visit, calling it "exceptional", adding:
"All states visits are important and this is one is both exceptional and historical.
"Because of the phenomenal success of the Queen's visit to Ireland in 2011, where she was made to feel very welcome, there is a sense that visit was a really important moment in the bilateral relationship."
"From the Queen down, everyone is wholeheartedly invested in the visit by the President and would like to return the hospitality. This evening's event kicks off that process."
This evening's invitees also included stalwarts of Britain's Irish community, like Tom Burke of the South London Irish Association and Alice Kennedy who runs the London Irish Pensioners Choir.
A group of UK-based Comhaltas musicians performed as the guests arrived to the reception, which began at 6pm.