Kelly Osbourne found returning to work for the first time since her son was born to be "one of the hardest things" she's ever done

She wrote on Instagram: "I have a new found respect for working mothers. I took my first job since having a baby. Having to leave him this morning was one of the hardest things I have ever done. This day can't go by quick enough for me. I can't want to have him back in my arms.(sic)"

Last month, Kelly expressed her frustration after her mother Sharon Osbourne let slip that her new grandson had been named after his father.

Sharon said: "She has [had the baby], yeah. Sydney. They're doing so so great. She won't let a picture go out of him and I am so proud of her."

Kelly later fumed on Instagram: "I am not ready to share him with the world. It is no one's place but mine to share any information about my baby!"

And During her pregnancy, Kelly's dad Ozzy Osbourne had struggled to keep the news that he was set to welcome a grandson a secret.

Kelly said: "I mean, he's told everyone ... the gender of my baby before I ever got the chance to."

But she admitted she thought it was sweet how excited the 'Paranoid' rocker was about having a grandson after her brother Jack only had daughters, Pearl, 10, Andy, seven, Minnie, four, and seven-month-old Maple.

She said: "I'm just like, 'Aww Dad, come on. Like, come on,' but I will say, every single day he does this little song and this little dance about how excited he is, and he is so excited that it's a boy. It's the first - out of me and my brother, it's the first boy, so, he's like planning all these things."

Ozzy is also grandfather to Isabelle, Kitty and Harry Hobbs, his and first wife Thelma Riley's daughter Jessica's children, and Elijah and Maia Osbourne, their son Louis' two kids.