The development was a brutal blow for the royal.

The new of King Charles’ cancer hospital dash only reached his youngest son after it appeared on the news, sources have claimed. It’s said Prince Harry was unaware of his dad’s health scare until the rest of the world knew as well.

On Thursday morning, King Charles was admitted to hospital, due to side effects caused by his current cancer treatment, but he was discharged later the same day.

The monarch has been undergoing weekly treatment for the disease since his diagnosis last February and returned full-time to work duties last April, The Mirror reports.

He was forced to pull out of engagements and completely cancel an away day in Birmingham to meet local communities today. But a palace aide described the King’s hospital visit to The London Clinic in Marylebone in London.

He was previously treated for a prostate condition at the hospital last January – as “a minor bump in the road” and insisted Charles’ treatment was still “very much headed in the right direction”.

In a brutal blow for his all-but estranged son Harry, the Duke was reportedly not informed about Charles’ hospital stay and side effect struggles before the Palace’s official announcement was released.

It comes the same week as Prince Harry finds himself embroiled in a bitter row surrounding his charity Sentable, which he has sensationally resigned from.

The Duke last saw his father, who has cancer, for a fleeting half an hour visit last February and relations between them remain strained.

We told last night how King Charles has cancelled engagements after being taken taken into hospital for observation, and had pulled out of engagements planned for yesterday afternoon, and a trip planned for today.

He was due to head to Birmingham to meet local communities, The Mirror reported, but sources close to him have passed off the scare as “a minor bump in the road”.

A palace aide said yesterday his treatment was still “very much headed in the right direction”. The King returned to full time duties last April but still maintained a reduced schedule in accordance with his weekly treatment at a London hospital.

Since then he has embarked on a major tour with the Queen in October to Australia and Samoa and continued his public duties at pace this year.

The King was at home in Clarence House yesterday evening, where he was said to be “in good form”, and was continuing to work on State papers and make calls from his study.

Buckingham Palace said it envisaged the King and Queen’s planned state visit to Italy commencing on April 7 would still go ahead as planned.

A statement from Buckingham Palace yesterday said: “Following scheduled and ongoing medical treatment for cancer this morning, The King experienced temporary side effects that required a short period of observation in hospital.”