Plum perfection! Duchess of Cambridge opts for a stylish peplum two-piece as she steps out for a mental health conference in London

• Kate wore Oscar de la Renta as she stepped out for a mental health conference
• The Duchess, 34, joined William for the Guild of Health Writers event
• Conference is being supported the Heads Together campign

The Duchess of Cambridge dazzled in an Oscar de la Renta creation as she stepped out for a conference in London on Monday night.

Kate, 34, opted for a peplum jacket and matching skirt from the luxury label at the Guild of Health Writers event, which focuses on mental health, with William, 34.

The Anxiety Epidemic conference is being supported by the Heads Together initiative, an umbrella campaign spearheaded by the Duke and Duchess along with Prince Harry.

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It aims to change the national conversation on mental well-being to a positive one and is the charity of the year for the 2017 London Marathon.

The conference, held at at Chandos House, will have a number of guest speakers including Paul Farmer, chief executive of Mind, which is one of the eight Heads Together charity partners.

William and Kate met with members of the Guild of Health writers tonight and heard from a Heads Together runner, and the Duke gave a short speech where he thanked everyone supporting the initiative.

'You may be wondering why Catherine, Harry and I got involved in this topic in the first place,' he said. 'Mental health is traditionally not a mainstream subject, after all.

'For me personally, it was a gradual awakening over many years through work I've been privileged to witness with vulnerable young people – the homeless, the unemployed, those who are unable to fulfil their potential. 

'It was their openness about their mental health, their anxiety issues, their honesty about not coping, that made me realise that poor mental health was a major issue in our society, much greater than anyone cared to admit.'

He added: 'It was an issue that needed addressing if we were to attempt to solve many other problems that trouble us.'

William announced they would be running a campaign over the coming months 'to get people from all walks of life to record videos recounting what it feels like to open up to someone else.' 

The videos are intended to 'inspire people across this country, whatever their background, to talk up, and to tell another person if they feel like they can't cope.' 

The Duchess' purple ensemble was her second outfit on a busy day of engagements, while her husband appeared to be wearing the same navy suit that he wore at an assembly for primary school pupils earlier in the day.

The engagements are on a landmark day for the royal family, as the Queen becomes the first British monarch to reach their Sapphire Jubilee - marking her 65-year-long reign.

There are no grand festivities planned to mark the head of state's milestone and the Queen is not due to be out and about on official engagements. 

Earlier, the couple attended an assembly with primary school pupils to mark the start of Children's Mental Health Week. 

Kate, who is patron of charity Place2Be which organised the 'Big Assembly', was joined by William for the visit to Mitchell Brook Primary School in north west London.

They presented a 'Kindness Cup' to the child who has 'has shown exceptional kindness in their school community and beyond' and meet staff and pupils.

Kate wore a strikingly similar outfit, a red peplum jacket and pencil skirt show off her slender legs, which she highlighted with a pair of heeled black court shoes.