Sharing a sensational throwback snap from one of their travels together, the mother-of-one could be seen smiling from ear to ear as she posed alongside her son in a leopard-print bikini on a luxury yacht.
WATCH: Elizabeth Hurley showcases dance moves in fun video
"Happy 19th Birthday to my beautiful baby @damianhurley1," she gushed in the caption, to which Damian replied: "I love you favourite twin, thank you for the best second lockdown birthday ever xxx."
The heartwarming post was flooded with messages, with Michelle Visage adding a string of birthday-themed emojis. Caroline Quentin remarked: "Happy Birthday you darling. Can't wait to see you when we can xxxx." Trinny Woodall added: "Happiest birthday darling D - hope to see you soon."
Despite it being Damian's second lockdown birthday, the aspiring model managed to mark the day with his famous mum in style - which included a fabulous firework display in their garden. "IT'S DAMIAN DAY!! happy birthday to meeeeee xxx," he wrote on Instagram.
Elizabeth shared this gorgeous throwback snap to mark her son's 19th birthday
As well as sharing a close bond with his mum, Damian is also following in her professional footsteps. He has taken the modelling world by a storm and has featured in a number of high-profile campaigns over the past few years.
The teenager has previously appeared alongside Elizabeth on the small screen after landing the role of Hansel von Liechtenstein, Crown Prince of Liechtenstein, in The Royals - his mum portrays the Queen in the popular drama.
Meanwhile, the mother-and-son duo have spent the majority of the COVID-19 lockdown at actress' estate but they have been bubbled up with some family members and friends, too.
The birthday boy posted this photo from his garden
The mother-of-one initially compared her family to The Waltons last year, when she exclusively spoke to HELLO! about life in self-isolation after being locked down at her country home in Herefordshire with eight people.
"We feel like the family in the Seventies TV show The Waltons," she told HELLO! at the time in an exclusive interview. "There are nine of us. I have my whole family here, including my mother, an aunt and a friend who has severe respiratory problems.
"I am completely paranoid that I won't be able to keep them safe, and I haven't let anyone leave the house apart from me. I just nip out to local food stores and wear a mask and gloves. I'm terrified of bringing the virus back to my vulnerable guests."
Make sure you never miss a story! Sign up to our newsletter to get all of our celebrity, royal and lifestyle news delivered directly to your inbox.