Imelda May has described performing the Irish national anthem ahead of Conor McGregor's fight against Floyd Mayweather as 'a proud moment' and a 'great experience'.

The singer relived the moment on The Late Late Show, telling host Ryan Tubridy that she was initially unsure if she could actually perform at the event, despite wanting to, due to a concert she had scheduled at a festival in England.

"I had a lot to think about, I wasn't sure if I was going to do it or not, or that I was going to be able to do it or not," May told Tubridy.

"In 27 years of doing this I have not cancelled a gig... I figured it was a festival and that people weren't just coming to see me."

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May revealed that the decision to pull out of the festival slot didn't come easily and that she sought the advice of her friends and family before deciding, as she didn't want to let anyone down, but in the end even the festival promoter gave her the go ahead.

"The promoter said, 'I'm really not happy about this, I really don't want to say this, but if I was you I'd go'," she said.

May said she felt the "call to Ireland to sing our national anthem" and wanted to "set up a great vibe for Conor".

"I went and I was very proud to sing our national anthem. I was 100% proud of that. I was thinking of my granny and my family, I was wanting to set up a great vibe for Conor before he went on," she said.

"It was just unbelievable and it felt like a proud moment," May added. "I had a great time, it was mental and it was a great experience."

Imelda May performing the national anthem at the McGregor fight