The mother of one of my oldest friends, who was always there with a shoulder to cry on when life got tough in our 20s and 30s, had a favourite saying. 'Keep your lamps lit, girls,' she used to say cheerfully, as we sobbed into our Earl Grey after yet another romantic disappointment or setback.

I've summoned that spirit more than once over the years, and it's always served me well.

Put on a brave face, get out there – and try to radiate positivity, even if it's the last thing you feel like doing.

Watching the Royal Family do their traditional Christmas walkabout at Sandringham this year, I was reminded of that sound advice.

The Prince and Princess of Wales and their three frankly delightful children weren't just keeping their own lamps lit after a very difficult year, but acting as a veritable beacon of positivity for everyone in the Royal Family.

These Christmas Day walkabouts can be very awkward and rather performative, and in recent years have felt somewhat doom–laden, especially as the older generation of royals has started to shuffle off this mortal coil.

But this year, as the Waleses met with well–wishers and a fresh–faced new generation took their place in the limelight, the miasma of gloom that had lately settled around the Monarchy seemed to evaporate like dew in the morning sun.

The Wales children were adorable, graciously accepting gifts and patiently doling out hugs and handshakes in return, especially young Charlotte, who was pretty as a picture in her neat little pea coat, glossy hair, big bow, sensible brown tights and ballet flats.

The Prince and Princess of Wales and their three frankly delightful children were acting as a veritable beacon of positivity for everyone in the Royal Family, writes Sarah Vine

Princess Charlotte and Mia Tindall attending the Christmas morning service at Sandringham

Posing happily for selfies and chatting to fans, they radiated wholesomeness and functionality as a family.

Quite a contrast to the week before, when a picture had been released from the Jeffrey Epstein files of Bad Uncle Andrew lying across the laps of five unidentified young women in the saloon room at Sandringham, a wolfish grin on his face, Ghislaine Maxwell laughing behind him.

That, plus the fact that the poor King had to make the decision, difficult no matter how inevitable, to cut his brother out of the family completely, might have easily overshadowed proceedings.

But it didn't, not even for a second. In fact, if anything, the atmosphere was the exact opposite. Thanks to the presence of those three beautifully dressed, beautifully mannered young royals and their equally charming Tindall cousins, it felt full of joy and hope for the future, a fresh new beginning after years of darkness, rancour and sorrow.