Party princess Bea hits town with Eugenie while glum mum Fergie dines with boyfriend just down the road

Princess Beatrice and Princess Eugenie hit the town last night to attend the launch of Form, a luxury menswear brand designed by Petra Ecclestone - the 19-year-old daughter of F1 mogul Bernie Ecclestone.

And their mum Fergie was also out and about, dining at The Dorchester with her Norwegian tycoon boyfriend Geir Frantzen.

The princesses smiled for the cameras at the event at Harrods in Knightsbridge and seemed to be having a nicer time than their mum who looked rather glum as she made her way home.

Pair of princesses: Eugenie and Beatrice last night at Harrods in Knightsbridge

The clothes launch was attended by Bernie Ecclestone, who has financially backed his daughter's business, his wife Slavica, racing car enthusiast Jay Kay and tennis star Boris Becker.

The royal sisters, no strangers to money or power themselves, looked poised and elegant but were in danger of being outshone by Petra and her sister Tamara who one day stand to inherit their father's £2.4billion fortune.

Super sisters: ( l-r) Eugenie, Tamara and Petra Ecclestone and Beatrice

On form: Bernie Ecclestone with Petra and wife Slavica at the launch last night

As her daughters mingled in Knightsbridge, Sarah Ferguson was in nearby Park Lane eating at China Tang at The Dorchester with boyfriend Geir Frantzen.

After they had eaten, the couple stood in the restaurant's hallway having a chat for about half an hour as their chauffeur-driven car waited for them.

They then emerged separately looking a bit serious, with Fergie even biting her nails as they drove away.

Glum: Sarah Ferguson and Geir Frantzen looked a bit down in the dumps as they left The Dorchester last night

Fergie nearly loses her skirt on windy family day out to the polo

In a knee length dress and white jacket the Duchess of York looked the image of respectability. Until the wind began that is.

As she walked across the polo field Sarah Ferguson's flimsy dress blew up, exposing her legs to the watching crowds.

Her quick reactions were all that stopped an embarrassing moment as she reached down to hold the skirt firmly in position.

Thigh-high: As Fergie picks her way across the mud she reveals her leg

The black and white wrap dress, decorated with musical notes, then slid to one side as the Duchess gingerly picked her way across a patch of mud in her white flip flops.

But the former wife of Prince Andrew didn't seem put out by her wardrobe malfunction.

Instead the 48-year-old was all smiles as she joined daughters Beatrice and Eugenie in cheering on the teams at the final of the Gold Cup polo match at the Santa Maria Polo Club in Sotogrande, Spain.

Oops: As her flimsy skirt flies up Sarah Ferguson only just avoids revealing all

The trio are enjoying a rare family holiday together to celebrate Princess Eugenie's brilliant A'level results and Princess Beatrice's recent 20th birthday.

The break may be the last time the three are together for a while. After receiving two As and a B at A' level 18-year-old Eugenie is expected to soon head off on her gap year abroad.

Meanwhile, Bea is gearing up to start a degree at Goldsmiths College in London next month after traveling around the world during her gap year.

Family day out: Fergie was with daughters Beatrice and Eugenie

It's not Ascot: The Princesses join a Mexican wave

Looking the image of her mother Bea chose a jewel green sundress, accessorised with a chain belt, white cardigan and an oversized brown leather clutch.

She and her sister wore of-the-moment black leather gladiator sandals, which Eugenie teamed with a blue sundress and turquoise cuff.

The young Royals were joined by a large group of friends to watch the polo.

The Royals were joined by their friends, including Bea's boyfriend Dave Clark, second from right

Dave, Eugenie and Bea urge on their team

Amongst the youngsters was Bea's boyfriend Dave Clark, who is said to have been given the seal of approval by her parents.

He certainly seemed to be getting along famously with the Duchess, laughing as she pulled a face at the match.

But it was Bea who really held his attention. She was introduced to the 26-year-old by her cousin Prince William, who attended St Andrews University with Mr Clarke.

What a liberty! Dave Clark laughs with Sarah Ferguson

So who do you think is going to win? Bea chats with her boyfriend Dave Clark