In the Garden Room at Clarence House, the Queen Mother receives her guests.

The Mayor of Volgograd is visiting to present her with an honorary citizen of his city.

Even at 100, she's still quite unstoppable Prince Charles

It is just one of dozens of private meetings she has, in addition to her public engagements.

Clarence House has been her London home since 1953 and has been witness to many of her birthdays.

Some of her staff have been with her throughout.

Though she talks to her daughter, the Queen almost every day, she is fiercely independent.

"She will consult the Queen, she won't necessarily do what the Queen wants her to do.

"Like perhaps, 'don't go out tonight if you're tired' is almost enough for her to go out tonight," her Lady-in-waiting, Dame Frances-Campbell Preston explains.

It is no secret that she has always enjoyed a drink and she hosts lavish lunch parties.

Though her own preference is for simple food like cottage pie, her life-style remains grand.

She always dresses for dinner, even if she is alone and loves to watch old videos.

"It's anything for a laugh, so she loves Dad's Army, Keeping Up Appearances and Yes Minister and Morse", says her niece, Margaret Rhodes.

But even though she has nearly a century of memories, she rarely dwells on the past.

"The other day she was talking about how she remembered as a child straw being put outside peoples houses so that carriages didn't make a noise going past. That kind of thing she will sort of throw out, but she won't bang on about it", says Lady-in-waiting, Dame Frances-Campbell Preston.

The rhythm of her life is unchanging. She moves between her homes in a rigid routine.

Beloved Scotland

As always, the next stop, after her birthday, will be Scotland and the Castle of Mey.

There, on the remote coast of Caithness, she takes a keen interest in her cattle and in all the local goings-on.

"She comes down to the farm and goes into the kitchen, and sits and has a yarn with my mum and yes, she catches up with all the gossip", says farm manager Danny McCarthy.

She finally gave up fishing in her eighties, but still loves the outdoor life, especially daily picnics at her favourite spot.

Margaret Rhodes recalls an earlier birthday present.

"I think it was for her 70th birthday all her family and friends gave her a wonderful log cabin down by one of the pools, so that is known in the Clarence House circles as the old bull and bush", she said.

And that typifies the Queen Mother's sense of fun.

Something she shares with her eldest grandson, Prince Charles.

In his words, even at 100, she's still "quite unstoppable".