The Queen’s granddaughter attributes it to the fact she was pregnant with daughter Lena Tindall at the time.
Harry and Meghan's wedding took place on May 19 last year.
Zara explained to the Daily Telegraph: “I was uncomfortable! My bum sort of slid over either side and Lena kicked the hell out of me for an hour.
“It just wasn’t comfy at all and it probably showed on my face.”
During the ceremony, Bishop Michael Curry gave an energetic speech which lasted 13 minutes.
Zara explained how this frustrated herm adding: “It was just the general amount of time everything was taking.
“I think my face was probably caught at the point when I thought: 'Right, he's going to finish now', and then he went off on another little story, and it was like, 'Really?’”
Zara Tindall went viral after images of last year's royal wedding (Image: GETTY)
Zara was pregnant with Lena Tindall at the time (Image: GETTY)
Lip readers claim Zara whispered to husband Mike Tindall: “I need the toilet.”
One day short of a month later the couple welcomed Lena.
Their fist daughter, Mia was born in June 2014.
Zara is 18th in the line of succession with Mia and Lena 19th and 20th.
READ MORE: Zara Tindall husband: Touching way Mike reassured wife during wedding