The Princess of Wales has revealed she is undergoing treatment for cancer in an emotional video message and told others battling the disease “you are not alone”.

Kate spoke about the “huge shock” of the medical development and how her family have experienced an “incredibly tough couple of months” and at times her voice cracked with feeling.

The princess was admitted to hospital for abdominal surgery on January 16 and at the time her condition was thought to be non-cancerous but tests after the successful operation found cancer, the type of which has not been disclosed.

The future Queen began a course of “preventative chemotherapy” late in February but is said to have a positive mindset for her recovery and is in good spirits, describing herself as “well and getting stronger every day”.

The King, who is also being treated for cancer, and the Queen have been told about the state of the princess’ health.

Speaking in the video message recorded on Wednesday in Windsor, the princess said: “In January, I underwent major abdominal surgery in London and at the time, it was thought that my condition was non-cancerous.

“The surgery was successful. However, tests after the operation found cancer had been present. My medical team therefore advised that I should undergo a course of preventative chemotherapy and I am now in the early stages of that treatment.

“This of course came as a huge shock, and William and I have been doing everything we can to process and manage this privately for the sake of our young family. As you can imagine, this has taken time.”

It is understood the video was released on the day William and Kate’s three children began their Easter school holidays to take advantage of the break to shield them from coverage of their mother’s health.

Kate, who is casually dressed in the video and sitting on a bench, added: “It has taken me time to recover from major surgery in order to start my treatment. But, most importantly, it has taken us time to explain everything to George, Charlotte and Louis in a way that is appropriate for them, and to reassure them that I am going to be OK.

“As I have said to them; I am well and getting stronger every day by focusing on the things that will help me heal; in my mind, body and spirits.”

The announcement may go some way to ending weeks of intense speculation and conspiracy theories on social media about the whereabouts and health of the future Queen.

It is not known how long Kate will be receiving treatment but it is understood she may be keen to attend events as and when she feels able to, in line with medical advice, although this will not indicate a return to full-time duties.