The Prince of Wales’s 60th birthday is proving to be much more enjoyable for him than his 50th. Ten years ago, in the aftermath of Princess Diana’s death, his unpopularity apparently knew no limits. Now a poll for this newspaper today shows people think he will made a good king and that he should be allowed to continue to speak out on issues of the day even when he succeeds to the throne.

The public has got it right. Charles has attracted ridicule for his public interventions on architecture, education, genetically modified food, climate change, sustainable communities and other issues. He has regularly been “a prophet without honour in his own land”. But he has also developed an infuriating record of being right and of latching on to important issues well before they have entered the main-stream. Whitehall has become accustomed to its royal penpal; the prince regularly nudging ministers and officials to heed his concerns.

His charities, especially the Prince’s Trust – established when he was just 28 – have achieved considerable success, most notably in rescuing young people from life’s scrap-heap. Long before government got into such programmes on any scale, the Prince’s Trust was there. Nearly three-quarters of those whom the charity helps find their way into education, training or employment, a record any politician would give his eye teeth for.

So he should be allowed to speak out, even on controversial issues, when he succeeds to the throne, even though protocol suggests this should not happen. The proviso is that nobody should feel constrained by that same protocol for criticising his views. An opinionated king should be ready for a robust debate.

But when will he succeed to the throne? The Queen, at 82, is already Britain’s oldest monarch. The Prince of Wales is now entitled to free off-peak bus travel and the winter fuel allowance. At an age when most people are winding down to retirement he has yet to take up the job for which he has been trained. If nothing changes in the next four years he will become the oldest person to succeed to the throne, beating William IV who was 64.

The laws of succession were not really intended for 21st-century longevity. The Queen has done a fine job but is it fair to ask her to continue doing it into her late eighties, nineties or, if she follows her mother’s example, beyond 100?

A mechanism should be found for Charles to succeed his mother while she is still alive. There would be a role for her, and a permanent place in the public’s affection, as King Mother. Her son, while he still has the energy and enthusiasm, would take on the hard work of being monarch. He has waited long enough.