The Duchess of Cambridge has spoken out following the Westminster terror attack that shocked the nation on Wednesday (22 March) as she conducted a royal engagement at a mental health event in London.

Kate Middleton, 35, spoke one day after the horrific incident which claimed four lives and left 29 people injured, with Isis claiming responsibility for the attack.

During a visit to raise the awareness of mental health – a passion she shares with husband Prince William – the mother-of-two expressed her sympathy to all those affected by the attack before beginning her planned speech at the event.

Kate Middleton
Kate Middleton said she was 'sending out thoughts and prayers to all those sadly affected by yesterday's terrible attack in Westminster' Yui Mok/Getty Images

She said: "Before I begin, I know you would all want to join me in sending our thoughts and prayers to all those sadly affected by yesterday's terrible attack in Westminster.

"We will be thinking of all the families, as we discuss the important issues we're here to talk about," she added.

The royal spoke to parents about how becoming a parent affected their mental health and, though she has a full-time live-in nanny to assist with her children Prince George and Princess Charlotte, Middleton was open about the difficulties of parenting.

Kate Middleton
Kate Middleton arrives at the Royal College of Obstetricians and Gynaecologists in London for the Best Beginnings charity launch of maternal mental health films ahead of Mother's Day Chris Jackson/Getty Images

On motherhood, she said: "Personally, becoming a mother has been such a rewarding and wonderful experience. However, at times it has also been a huge challenge – even for me who has support at home that most mothers do not."

The duchess wore a 60s inspired coral tweed skirt suit by Eponine for the daytime charity engagement today (23 March), which we have previously seen on her in March 2016. She accessorised the springtime ensemble with a gold LK Bennett clutch bag and nude court shoes.

Middleton remained poised throughout the visit to Best Beginnings in aid of launching a series of educational films about maternal mental health.

Kate Middleton
Kate Middleton arrives at the Royal College of Obstetricians and Gynaecologists in London Chris Jackson/Getty Images

Best beginnings is a charity partner of the Duke and Duchess of Cambridge and Prince Harry's Heads Together mental health awareness campaign. The launch was also attended by health campaigners, academics and professionals at the Royal College of Obstetricians and Gynaecologists in central London.

Middleton's visit comes as Queen Elizabeth II postponed her planned visit to open the new headquarters of New Scotland Yard, with Buckingham Palace announcing last night: "In light of today's events the decision has been taken to postpone the Queen's engagement to New Scotland Yard." Her Majesty is said to be remaining inside Buckingham Palace while police patrol outside the gates among milling tourists.

Kate Middleton
Kate Middleton arrives at the launch of maternal mental health films ahead of Mother's Day at Royal College of Obstetricians and Gynaecologists in London Chris Jackson/Getty Images