Britney Spears cried "tears of joy" on her 40th birthday

She wrote on Instagram: "I’m so blessed and grateful !!!! Tears of joy today ?? … Thank you for all the b-day wishes !!!!

“Psss I didn’t even drink the champagne no lie !!!!”(sic)"

Britney also used her birthday to take another opportunity to have a swipe at her family - including her father, Jamie Spears, who served as her co-conservator - for not allowing her to make her own decisions.

She wrote in a separate post: "I’m not turning 40 … I’m turning 4 and if any of you haven’t HEARD … I did almost 250 shows in Las Vegas for 4 years and went out twice !!!! With that said … I think I will have to put on my hot little dresses on every night for the rest of my life to break even for working for my family my whole life with only old songs permitted !!! More classic fashion dresses coming soon to my Instagram … by me … worn by me … and in the meantime, kiss my beautiful white ass ‘Murica !!!!!!(sic)"

Britney jetted off on vacation with her fiance Sam Asghari to celebrate her birthday and the 27-year-old fitness trainer marked the 'Circus' singer's milestone birthday with a sweet tribute on Instagram.

He wrote: "I call you Lioness because I admire your relentless strength, I’m inspired by your beautiful heart, I celebrate your smile that lights up my world. Everyday is your birthday my queen Happy 1st birthday to my wife #dec2nd"(sic)"

But Sam also ruled out speculation that the pair have already married by noting in the comments: "I also been calling her wife since day 1 (sic)