Katherine Jenkins thinks Britain's Queen Elizabeth has a "great sense of humour".

Katherine Jenkins

Katherine Jenkins

The 34-year-old opera singer has performed for the 89-year-old monarch several times and admires her "dedication and energy".

She said: "I've been fortunate enough over the last decade to sing for the queen and meet her a quite a few times.

"I really admire her amazing dedication and energy and think she has a great sense of humour."

Katherine - who is expecting her first child with husband Andrew Levitas - found it very funny when the queen made an unscheduled appearance at a press conference announcing the singer will be performing at the monarch's 90th birthday celebrations at Windsor Castle's Home Park next May as she was on her way to the Windsor Horse Show.

She laughed to Britain's HELLO! magazine: "You should have seen all those royal correspondents - their jaws hit the floor as she strolled past."

The mezzo-soprano previously admitted she was "honoured" to be involved with next year's event.

She posted on Instagram "Honoured to have been asked to perform at Her Majesty The Queens 90th Birthday Celebrations Next May.(sic)"