As the £15 crackers contained gunpowder, Ivy and Bert Francis were told they would have to give their names and addresses. A message had popped up on the assistant's till screen asking for the details.
Ivy, 82, and Bert, 83, couldn't quite believe what they were hearing, and asked to speak to a supervisor.
Ivy told The Daily Express: "We felt sorry for the assistant. She called her supervisor over and was told the message on the till screen was correct.
"It was laughable really. She said, 'I am sorry, we have to ask.' We were shocked to be honest, we couldn't believe it when she asked us and she ended up taking down our names and addresses.
"We thought it was very strange. I thought, 'Who do you think we are, Guy Fawkes?'
"I'm not sure what she thought we were going to do with them. We will enjoy them on Christmas Day with a little smile."
In the UK, crackers can't be sold to anyone under 12.
A spokesperson for M & S said it's not company policy to take personal details when selling crackers, and that it was a technical error on the till system.
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