"Happy May Day," the couple's team wrote below the video Kate Middleton and Prince William are teasing their next project. On May 1, the Prince and Princess of Wales' office at Kensington Palace posted a mysterious new video to their social media accounts.

While Princess Kate and Prince William have always marked the milestone in private, this year they're on two-day Scottish tour.

Kate Middleton joined husband Prince William for the couple’s royal visit to Scotland on Tuesday. The Prince and Princess of Wales kicked off a two-day visit to the Isles of Mull and Iona. Tuesday’s outing also falls on the same day as the royal couple’s 14th wedding anniversary.