TENNIS coach Judy Murray has sparked a new legal tender debate after staff in a London bakery refused to take her Scottish £10 because it wasn't "British" currency.

Ms Murray, mother of Wimbledon winner Andy, said that she had been trying to buy two doughnuts for £9 but had been unable to complete the purchase because staff wouldn't accept her cash.

READ MORE: Why Scottish banknotes can be rejected 

Tweeting a picture of a solitary confection, she said: "When you go to pay £9 for 2 donuts (yes, really) in London and your £10 Bank of  Scotland note is refused because “we only take British ones”.

Her social media followers rallied to her defence, pointing out similar stories and saying that Scottish banknotes are legal tender. 

READ MORE: Video - watch rugby fan being refused sale of scarf because he wanted to pay with Scottish money

One said: "We accept yours’ I once told a sales assistant in Debenhams Bury when she wasn’t going to take my Scottish £20 note. She took it then."

Another added: "I’d have left the Scottish note on the counter and left. It’s legal tender so you’re not refusing to pay. How ignorant", while Ms Murray was also advised to have taken a bite out of one of the doughnuts and asked if they would 'take her money now?'

HeraldScotland:

Cake fan and coach Judy Murray

The Scottish coach makes no secret of her love of cakes, often Tweeting pictures of her desserts and sweet snacks to her legion of followers.

READ MORE: Dubai bureau offers different exchange rates for 'Scottish pound' and pound Sterling

Technically, Scottish banknotes are not, in fact, legal tender anywhere in the UK - even Scotland. But they have been accepted as legal currency for centuries.