The Princess of Wales has spoken of her relief at completing her course of chemotherapy, in a highly personal video released by Kensington Palace, BBC reports.

Catherine revealed in March that she was undergoing cancer treatment and has been out of sight of the public for much of this year.

She will be carrying out a few engagements this year, which could include Remembrance events in November and her annual Christmas carol concert.

But in an emotional video message she says this year has been "incredibly tough" and "that life as you know it can change in an instant".

This latest update on Catherine's health sends a positive message about her progress, but there is a long road still to go.

Kensington Palace has indicated it is not possible at this stage to say whether she is cancer-free.

The princess describes the "stormy waters" of her experience of cancer as "complex, scary and unpredictable".

"With humility, it also brings you face to face with your own vulnerabilities in a way you have never considered before, and with that, a new perspective on everything," says the princess, in an unusually personal video filmed last month in Norfolk.

The video, shot in autumnal colours, suggests how pleased she is to have completed this stage of her treatment.

"As the summer comes to an end, I cannot tell you what a relief it is to have finally completed my chemotherapy treatment," she says, seen driving and walking with her family.

The princess is expected to return for a "handful" of visits later this year, perhaps including the annual Remembrance service at the Cenotaph.

But palace sources also emphasise that there is still a long way to a full return and that the princess will make her health her main focus for the next few months.

"My path to healing and full recovery is long and I must continue to take each day as it comes," she says.

She says despite the tough times her experience has given her a "renewed sense of hope and appreciation of life".

Catherine has been in recovery and away from public duties for much of what has been a difficult year.

Her health problems began in January when she was in hospital for an unspecified type of abdominal surgery.

A cancer diagnosis was then revealed by the princess in March, with a video message saying that she was undergoing treatment and would need privacy while she recovered.

Catherine described it as a "huge shock" after an "incredibly tough couple of months".

Her first public appearance of the year came at Trooping the Colour in June, when she waved from the Buckingham Palace balcony.

Ahead of that appearance the princess had issued a personal statement of cautious optimism, announcing her return but saying she was "not out of the woods yet" and had "good days and bad days" with her cancer treatment.

Her most recent appearance was in July when she was given a standing ovation at Wimbledon when she attended the men's singles final.