He wrote for the Mail: “In the event [Easter Sunday], he did not merely swap pleasantries. This was a full-scale, traditional royal walkabout with – crucially – handshakes. And not just one or two.
“If proof were needed that our monarch is getting better, then here it was.
“He didn’t just look well but he was manifestly enjoying being back among his people, greeting a long line of well-wishers from as far afield as New Zealand and the USA with an outstretched, ungloved hand.
“Even the late Queen, when in the rudest of health, did not undertake Easter Sunday walkabouts like this. The routine was always the same: a chat with the Dean of Windsor, a posy from a child or two, a wave to the waiting crowds and back to the castle.”
The expert added: “No one is being complacent. Palace staff are making it clear that the King’s cancer treatment is still ongoing and that potential royal attendance at any event will be reviewed on an individual basis.
“However, this was the clearest indication yet that we are going to see more, not less, of the monarch as we enter the royal peak season.”
Mr Hardman said that the next positive indicator for the monarch’s health could be a trip to Scotland.
He claimed: “The next positive signal should be when we see the King back at his beloved Birkhall. He has not been in the Highlands since his diagnosis, given the need to be within easy reach of his doctors.
“Should we spot him up on Deeside in the weeks ahead, we will know, for sure, that things really are on the up.”
