King insists 'I'm alright, thank you' as he's asked about his cancer treatment ... trends now

King Charles III today insisted 'I'm alright, thank you' after being asked how his cancer treatment was going as he returned to public duties by visiting a hospital.

The monarch looked overjoyed to be back today for the first time since his cancer diagnosis, smiling and holding the hands of patients on a chemotherapy ward.

His Majesty – who still has the disease and is undergoing treatment - visited the University College Hospital Macmillan Cancer Centre in London this morning with his wife Queen Camilla, meeting patients and staff in his role as the charity's patron.

Charles is keen that his inaugural engagement since doctors gave him the all-clear to restart public events will raise awareness of the importance of early diagnosis.

The 75-year-old monarch also hopes the trip can highlight some off the innovative research, supported by Cancer Research UK, which is taking place at the hospital.

And today it can be announced that His Majesty has agreed to become the new patron of Cancer Research UK, bringing his own ongoing experience to the position.

The hospital was not chosen because it has a link with the King's treatment or form of cancer, neither of which have yet been publicly disclosed by Buckingham Palace.

Also today, Prince William visited an Earthshot Prize finalist firm in Seaham, County Durham on an engagement while his wife Kate's cancer treatment continues.

The centre provides facilities for the diagnosis and treatment of a wide range of cancer and non-cancer conditions, whilst also supporting patients and their families.

Ahead of the King and Queen's arrival, a small group of die-hard fans gathered after news of the visit leaked out.

John Loughrey, 69, a well-known royal superfan from Streatham, South London, bought roses to give to the King.

'I am going to tell him I have been praying for him and what a brilliant job Queen Camilla has been doing for him,' he said.

Mr Lougrey said he had lost his own partner, Marion, to skin cancer 21 years ago just two months after she was diagnosed. He added: 'I know exactly what the King and Queen are going through. I've experienced it with the loss of my partner 21 years ago, too.

'The King hasn't kept his diagnosis to himself but has shared it with the nation to encourage people to get diagnosed. I'm going for a check-up myself next week, so he has encouraged me to do that too. I want His Majesty to know how much he is appreciated and that the Queen is his foundation.

'I am also praying for the Princess of Wales and everything she is going through too.'

A royal aide said the visit had been arranged in the hope it would encourage others to be open about their cancer diagnosis and raise awareness of the benefits of early diagnosis.

They added: 'He also wants to show it is possible to work with cancer, although he appreciates that everyone has their own journey and it is not for everyone. '

The King and Queen were met by University College London Hospitals (UCLH) chair Baroness Julia Neuberger and chief executive David Probert.

Inside the centre, the King and Queen spoke to clinicians and heard more about the use of innovative technology at UCLH; including CT scanners which are being used to help with the early detection of cancer.

As the new patron of Cancer Research UK, His Majesty met the charity's chief clinician, Professor Charlie Swanton, who has led on a project called TRACERx - a collaboration with 250 researchers and clinicians based at 19 centres across the UK.

The project is the single biggest investment in lung cancer research by Cancer Research UK and aims to investigate how lung cancer evolves over time and why treatments sometimes stop working.

After meeting patients and their families who receive treatment at the centre, the King and Queen were due to have an opportunity to meet hospital staff and supporters of the UCLH Charity, Macmillan Cancer Support and Cancer Research UK.

Before departing, Charles and Camilla were due to be presented with posies by young patients.

In 1997, as Prince of Wales, the King become patron of Macmillan Cancer Support, which provides a range of support to people living with cancer and promotes better cancer care.

In addition to the King's new Patronage of Cancer Research UK, The Duke of Gloucester and Princess Alexandra are also joint presidents of Cancer Research UK.

Since 2008, Camilla has been president of Maggie's which provides free expert care and support in centres across the UK and online to everyone with cancer as well as their friends and families.

Since becoming president, Camilla has visited 17 centres across the UK, including opening the Maggie's Royal Free in London earlier this year in January.