The 36-year-old actress married David, 70, in London in 2019, and she took to Instagram on Sunday (28.06.20) to post a glowing tribute to her husband, describing him as the ''love of [her] life''.
Alongside a series of behind-the-scenes wedding photographs and a video, Katharine wrote: ''A year ago today I married the love of my life. Thank you for always loving me and inspiring me in all aspects of my life. I love you. Here's to the future! (Oh and happy anniversary to the other love of my life - this dreamy dress! (sic)''
David also posted about their one-year wedding anniversary on Instagram.
Alongside a picture of them together, he wrote: ''happy anniversary to the love of my life!! (sic)''
David previously described his wife as the ''whole package''.
The singer tied the knot with the 'Scorpion' star following a 12-month engagement, and he feels incredibly lucky to be able to call her his spouse.
He said of Katharine: ''She's the whole package, you know? Singing, acting, beauty, she's got it all!''
Shortly after their wedding, Katharine decided to take David's surname because she loves the ''traditional'' nature of taking a partner's last name.
Asked why she decided to adopt her husband's surname, she previously said: ''I'm a romantic. I've always liked the idea that it's still a traditional thing that exists in our society. I like the idea.
''I think it's romantic and it's a great last name ... We've been away since we've been married, so not [yet], but I love it. I just love the ring of it, so I'm enjoying it.''