Prince William was cheesin' big time at a royal outing, just a day after his wife, Kate Middleton, revealed to the world she's in cancer remission.

William attended the inaugural Emergency and Critical Care Conference in Birmingham, England on Wednesday ... rocking his new title as Patron of the College of Paramedics -- a role that hits home after everything Kate's been through.

William mingled with College of Paramedics leaders from all corners of the field -- the whole initiative dedicated to making sharp calls in high-pressure situations. William likely drew on his experience as a Royal Air Force search-and-rescue pilot and with the East Anglian Air Ambulance crew to connect with the paramedics.

Kate made a rare appearance at London’s Royal Marsden Hospital the day before, unveiling her new role as Joint Patron, to back their medical research and help transform the lives of cancer patients.

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Her new role came as she announced she's in remission, following a tough year when she stepped back from public life to go through chemo. She's kept the type of cancer under wraps.