Team HeadsTogether runners ahead of the London Marathon on Sunday.

Every runner has a different reason for participating in the marathon, and today Kate is talking to them about what inspired each of them to join.

On the Heads Together website, you can read about some of the runners and their specific stories and motivation behind joining Team Heads Together. Whether they are running on behalf of somebody they know who is struggling with mental health, or whether they themselves have experienced difficulties, all the runners share the same motivation: to help raise awareness that mental health is something to be talked about and not hidden.

While all the runners are wearing Heads Together headbands, 70 Royal Mail post-boxes along the London Marathon route will also be wrapped in a headband, one of which the Duchess revealed at the Palace today.

It will be a year this coming May since the Royal Trio launched the Heads Together campaign, aimed at targeting stigma surrounding mental health.

During this time we have seen countless people share their experiences of battling various illnesses, and most recently William and Harry expressed their struggles with dealing with the loss of their mother, Diana.

Heads Together is the London Marathon's chosen charity of the year, and Sunday's race will be the biggest expression of the project yet, with 39,000 participants wearing the Heads Together headband to raise awareness about mental health at an even bigger scale.

"Through their work with young people, emergency response, homeless charities, and with veterans, their Royal Highnesses have seen time and time again that unresolved mental health problems lie at the heart of some of our greatest social challenges,” the Palace stated.

Outfit details:

Kate's definitely a Breton stripe fan! Today she added yet another striped top to her wardrobe: this one is by a brand she has worn before, Luisa Spagnoli. Kate has owned their gorgeous red skirt suit since 2011 which has been worn multiple times. This jumper is her second item of theirs that she owns. It is their 'Muvi Pullover' which retails for £220/$280, and while Kate's colourway is no longer available, both the navy and yellow versions are. The ribbed knit is 100% pure wool.

Kate was also wearing her Superga Cotu Classic sneakers in white which are available at Superga, Zappos, ShopBop and Nordstrom, to name a few, for £50/$65. They are also on Amazon for a cheaper price that varies depending on your size.

Kate looks to be in her black Zara mid-rise, ankle length 'Body Curve Jeggings', available for £25.99/$35.90.

It was back to her favourite earrings for causal appearances: Kiki McDonough's Citrine Classic Pear Drop Earrings. These 18ct yellow-gold earrings are available on the Kiki website for £495/$630.

In the photo above you can see Kate is wearing a microphone on her top—they must be taping something for the future we don't know about yet.