Yet another poll about succession 8/12/17

[sandy]

If the polls still give her low numbers I think he'll tread cautiously.

[TLLK]

No regency, etc

Well there could be one if QEII should suffer a debilitating illness or other health issue and the government appoints Charles as her regent. They were much more common centuries ago because the chance of a monarchy dying early were greater. However now it is possible that it would be used if the monarch were to be taken ill for a lengthy period of time and couldn't fulfill their duties.

The Regency Act from 1937 details-

The Regency Act 1937 made general provision for a regent in the event of a monarch becoming incapacitated. It states that the monarch's duties will be performed by a regent if the monarch is declared in writing to be incapable of performing royal functions by three or more out of the sovereign's wife or husband, the Lord Chancellor, the Speaker of the House of Commons, the Lord Chief Justice and the Master of the Rolls.

The Act states that the regency should only last until the monarch has recovered his or her health.

It also makes provision for children under the age of 18 succeeding their parents, stating that the next person in the line of succession over the age of 21 (later lowered to 18) will act as regent until the monarch comes of age.

[sandy]

Well right now there is no need for a regent.

[amabel]

No but it is possible at the queen's age, that she might be unwell for some time and not abel to work. I should think she'll go on till she drops but at her great age, ill health could leave her weak and not able to fulfil her duties...

[sandy]

Some ninety plus year olds are still going strong. It all depends on the person. Elizabeth is of course not doing the same number of appearances as she used to.

[TLLK]

No but it is possible at the queen's age, that she might be unwell for some time and not abel to work. I should think she'll go on till she drops but at her great age, ill health could leave her weak and not able to fulfil her duties...

I agree @amabel and therefore the Regency Act wisely allows her to maintain her title as the monarch while a regent (most likely Charles) can take on the duties associated with the role.

Even with QEII's excellent health, she is in her ninth decade.