Singer Amy MacDonald has apologised to fans of Scottish football for forgetting the words to the national anthem before last night's World Cup qualifier against Wales.

The 25-year-old, who previously had trouble with the song before a match against Liechtenstein in 2010, has admitted that she was "nervous" about performing in front of 40,000 people.

"I know the words but don't know anyone who could go on to a pitch in front of 40k and not get nervous. Sorry, I'm not perfect," she wrote on Twitter. "Always so proud to sing our anthem. Sorry for nerves — hope passion came across."

Scotland went on to lose the match at Hampden Park 2-1.