The heir, 73, agreed at short notice to throw his weight behind the booster campaign by visiting the walk-in centre. Charles told volunteers in Kennington, south London: “You are marvellous. What would we do without you?”

       And having recently had the booster himself he criticised anti-vaxxers, saying: “It is so frustrating all these nonsense conspiracy theories.”

       Speaking to those resting after the jab, he said: “So many marvellous people have been volunteering. I am glad you didn’t have to wait too long.”

       He also spoke to Kate Suiter, a former picture editor who trained eight months ago to be a vaccinator.

       Afterwards she said: “He said thank you for helping and I joked that I had the gift of the jab and he laughed and said ‘I’m going to use that.’”

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