In the exclusive interview and photoshoot out this week, the Hollywood siren said she screamed with joy when she discovered she was about to become a grandmother.
She skipped panto in the UK for the first time in over 17 years so she could spend the holiday with her son Nicholai, daughter-in-law Alison and grandson Cash, telling HELLO! "I starred as ‘grandmother’ in my own Christmas production. It’s my best one yet!"
Britt, 71, who was present at the birth, added: "They told me very early on. I’m very good at keeping things private, but I wanted to scream the good news! As soon as they told me it was OK to announce, I went into full-on ‘grandma mode'."
"When I first saw the baby he was so tiny. I thought: ‘Oh my God, maybe I’ll break him!’ Within one day, my instincts came back and knew exactly what to do.
"I come around every Saturday at 8am – I have my own keys so I let myself in. I take Cash, and Nic and Alison go back to sleep. I lock myself in his room and speak to him in Swedish! He’ll call me ‘farmor’, which means ‘father’s mother’ in Swedish."
Her son Nic, whose father was Lou Adler, also tells of his close relationship to his mother despite his unconventional upbringing.
"I’m learning more about what kind of mother she was now she’s a grandmother, as she was doing a lot of movies when I was young. Mum always wanted me to sit up straight, smile and be respectful, dress smartly… maybe because we were in the public eye, she was concerned how we appeared to the outside world, but she always cared about me.
"I had to sit mum down and tell her: ‘You were the best mother ever’. She really was."
Britt, who is also mother to Victoria by Peter Sellers and T.J. from her marriage to Slim Jim Phantom, also talks for the first time of her regret over her plastic surgery procedures.
When asked do you wish you’d grown old gracefully she admitted: "Yes, I do. I’ve realised this is just not me, but it is what it is and you have to live with it.
"Whatever I did 15 or 20 years ago, I’d never have done now. I turned 50, and you get insecure. The funny thing is for the last few years my career has been in the theatre, and natural expression is seen as a good thing! I think people look so much better if they don’t have surgery."
Read the full interview in HELLO! magazine, out now.