Charles delivered the remarks in a recorded message which will be aired at the ancient Maundy Thursday church service at Worcester Cathedral in central England which the 75-year-old king will miss due to his illness.

"In this country, we are blessed by all the different services that exist for our welfare," he says in the message which was recorded along with a bible reading earlier this month.

"But over and above these organisations and their selfless staff, we need and benefit greatly from those who extend the hand of friendship to us, especially in a time of need."

The recording was made before his daughter-in-law, Kate, the Princess of Wales and wife of his eldest son Prince William, issued a video message in which she revealed she was having preventative chemotherapy after cancer was discovered in the aftermath of abdominal surgery in January.

While Charles will miss Thursday's event, he is due to join other members of his family on Sunday at a scaled-down Easter Sunday service at Windsor Castle, his first public appearance at a royal event since it was disclosed in February he was suffering from an undisclosed form of cancer.

As she has done at other recent engagements, Queen Camilla will step in for the king at the traditional Maundy service, presenting 75 men and 75 women, to mark the king's age, with two small purses containing symbolic gifts of specially minted coins.

The custom, which dates back centuries, recognises recipients for their outstanding Christian service from across the country.

"It is for me a great sadness that I cannot be with you all today," Charles says in his message. "This act of worship here in Worcester Cathedral reminds me of the pledge I made at the beginning of the coronation service, to follow Christ's example, not to be served, but to serve.

"That I have always tried to do and continue to do with my whole heart."