King Charles joked he was “past my sell-by date” as he packed dried fruit at a female-run Indian restaurant alongside the Queen yesterday.

The monarch, 76, was so quick at packing dates into bags that he was asked to come back and do the job each year. Laughing, he quipped: “I may be past my sell-by date!”

The royal couple were in high spirits as they visited Darjeeling Express on London’s Carnaby Street on Wednesday afternoon at an event to mark the start of Ramadan on Friday.

During their visit, the pair met staff and leading British Muslim women including circuit judge Khatun Sapnara, crime author Saima Mir, Masterchef winner Saliha Mahmood Ahmed and businesswoman Shaheen Sayed of Accenture.

The Queen then made her way to the kitchen to help staff who were packing up boxes of biryani which will be sent to Doorstep, a charity which assists families by providing goods and services to make their lives more comfortable as they await a permanent housing solution.

It is part of Darjeeling Express’ commitment to cook for charitable causes every Ramadan.

Wielding a large spoon, Camilla helped ladle a portion into a takeaway box and said: “Is that enough or some more? They might still be a bit hungry after my portion.”

The Queen then went in search of her husband to help, even though he was busy chatting to guests and wasn’t due to participate.

Waving a takeaway box, she coughed loudly to get his attention, and after Charles spotted the commotion he good-naturedly came over.

“Is it chicken and proper basmati rice?” he enquired as he happily got stuck in ladling too. The King appeared delighted when he was told some was being sent to the Palace for them to eat later.

The couple then sat down to pack dates into white paper bags that will be sent for Iftaar (the fastbreaking evening meal) to hospitals during the Muslim holy month.

Traditionally, dates are eaten as the first food to break the fast at sunset, following the example of the Prophet Mohammed.

Charles was packing them so fast that restauranteur Asma Khan said: “You are packing them faster than I can seal them! I never realised this was such a speedy couple. We have a relay going on here.”

The comment left him giggling.

During Ramadan, Ms Khan donates the restaurant’s entire proceeds to charity and sends food packages to hospitals as part of the Zakat al Fitr, an obligatory charitable donation of food to the poor and needy before the end of Ramadan.

After the joint visit, the King joined a discussion with members of the British Syrian community at Imad’s Syrian Kitchen, also in Carnaby Street.

The Quene meanwhile travelled to Buckingham Palace where she hosted a reception with finalists, judges and celebrity readers to celebrate the final of BBC’s creative writing competition, 500 Words.