Speaking to The Telegraph after Sir Keir was taken away by his entourage, Paul Stoner explained why he had made the unusual offer.
The 60-year-old said: “I asked him if he wanted an apple and when he said ‘yes’ I gave him a lemon because I think he’s joking.
“When you call someone a lemon, you think they’re a bit of an idiot, a bit of a sour.
“He didn’t even know it wasn’t an apple. He just looked confused and said ‘thank you’.”