Happy birthday Pippa! Miss Middleton starts early birthday celebrations by cheering Andy Murray to victory in a summery yellow dress

Happy birthday Pippa! Miss Middleton starts early birthday celebrations by cheering Andy Murray to victory in a summery yellow dress

The Duchess of Cambridge's sister wore a vibrant yellow dress and nude wedges

Took seat next to Spencer Vegosen for second day running

Socialised with Roger Federer's wife after watching him lose in the semi-finals

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UPDATED:

11:09 GMT, 6 September 2012

Pippa Middleton celebrated her 29th birthday in style last night, by cheering Andy Murray to victory in the US Open quarter-final.

The Duchess of Cambridge's sister donned a vibrant lacy yellow dress, nude wedges and carried a straw handbag at the match.

Once inside the courts she promptly took
a seat next to dark-haired, 6ft 3in Spencer Vegosen – a Harvard
graduate and accomplished tennis player – before watching the men's quarter final game unfold.

Pippa Middleton and Spencer Vegosen watched Andy Murray play in the men's quarter finals

Pippa Middleton and Spencer Vegosen watched Andy Murray play in the men's quarter finals

Avid tennis fan Pippa looked like she was enjoying the game, it was her second day at the tennis

Avid tennis fan Pippa looked like she was enjoying the game, it was her second day at the tennis

Avid tennis fan Pippa looked like she was enjoying the game, it was her second day at the tennis

Pippa wore a lacy yellow dress and had her hair in loose curls as she took her seat next to Harvard graduate Spencer

Pippa wore a lacy yellow dress and had her hair in loose curls as she took her seat next to Harvard graduate Spencer

It is not the first time that Pippa
has taken a seat next to Mr Vegosen, they both cheered Roger Federer to
glory just a day ago on day nine of the competition.

Mr Vegosen, who now resides in New York but is originally from Illinois, Chicago is a familiar face on the sporting scene and he was
once one of the top junior tennis players in the U.S, winning 11
sportsmanship awards. His father Jon is also president of the U.S.Tennis
Association.

It is believed Mr Vegosen
received a BA in East Asian studies and mathematics from Harvard
University and spent last summer working in Hong Kong as an analyst for
Goldman Sachs. However it is not known where he currently works.

The pair laughed and joked together at the USTA Billie Jean King National Tennis Centre in Flushing, Queens, New York.

Pippa smiled as she watched Murray play and was joined by a brunette friend

Pippa smiled as she watched Murray play and was joined by a brunette friend

Pippa was also joined by a brunette
friend and the two seemed in high spirits as they clapped and cheered on
the Scottish player who, from
the dire straits of 6-3, 5-1 down when he could barely get the ball in
the court, fought back to win 3-6, 7-6, 6-2, 6-0 in three hours
to keep his Grand Slam dream alive.

After finishing he was able to relax
and see who his next opponent would be in his second straight semi-final
at Flushing Meadows — whether it would be a rematch of his epic two
clashes with Roger Federer at Wimbledon this year or a less expected
contest with Czech powerhouse Tomas Berdych.

In
the end Berdych shocked Federer in four sets and Murray now has two
days to compose himself after making what was an awkward assignment
against the 6ft 6in Croat look exactly that.

Avid tennis fan Pippa also attended the match between Tomas Berdych and Roger Federer, as his guest of honour in his box.

Pippa, who turns 29 today, watches the men's singles quarterfinal match between Roger Federer of Switzerland and Tomas Berdych of Czech Republic

Pippa, who turns 29 today, watches the men's singles quarterfinal match between Roger Federer of Switzerland and Tomas Berdych of Czech Republic

Pippa Middleton attended the US open quarter final and took her seat in Roger Federer's private box and cheered on the Swiss player

Pippa Middleton attended the US open quarter final and took her seat in Roger Federer's private box and cheered on the Swiss player

Roger Federer cut a disconsolate
figure as he tried to come to terms with his shock quarter-final exit
against an inspired Tomas Berdych at the US Open.

Not
since 2003 had Federer lost before the semi-final stage at Flushing
Meadows, winning five titles in that time, and he went into the
tournament on a high after a stellar summer.

Pippa was spotted after the match bonding with Federer's wife Miroslava Vavrinec Federer as they left the stadium.

Since landing in the metropolis on Saturday to attend meetings about her
upcoming book, Celebrate: A Year of Festivities for Families and
Friends, Pippa has been snapped with a number of men while sampling some
of New York's finer delights.

Pippa wore a bright yellow dress with nude wedges and carried a straw handbag as she left the match

Pippa wore a bright yellow dress with nude wedges and carried a straw handbag as she left the match

Pippa wore a bright yellow dress with nude wedges and carried a straw handbag as she left the match

Pippa was seen socialising with Roger Federer's wife Miroslava Vavrinec Federer at the US Open Tennis Center in New York City after the game

Pippa was seen socialising with Roger Federer's wife Miroslava Vavrinec Federer at the US Open Tennis Center in New York City after the game

In an opulent welcome hotelier Andre Balazs, who is reportedly worth
more than $450 million, flew her by seaplane – a trip that costs $525
for a single journey – to his resort, Sunset Beach, on Shelter Island on
Sunday.

And later that evening the New York Daily News reported that she was
spotted at the Electric Room at Dream Downtown in the Meatpacking
district with former New York Ranger Sean Avery.

'She was only there for a short time,' a source told the paper, adding
they were there with Mazdack Rassi, owner of photography company Milk
Studios.

It has been suggested that Pippa is staying at the Carlyle Hotel located
in the Upper East Side, where Roger Federer also has a suite, with two
friends, where rooms start at $600 and reach $15,000 – without taxes.

Her trip, during which she is apparently courting the perks of fame, come despite her demands to remain out of the public gaze.

Pippa scored a style ace the day before when she watched Samantha Stosur of Australia play Victoria Azarenka of Belarus during the quarterfinals match

Pippa scored a style ace the day before when she watched Samantha Stosur of Australia play Victoria Azarenka of Belarus during the quarterfinals match

Pippa scored a style ace the day before when she watched Samantha Stosur of Australia play Victoria Azarenka of Belarus during the quarterfinals match

While newspapers have respected her request to be recognised as a
private citizen, she still very much seems to be enjoying the
high-flying life of a socialite.

Despite her request, U.S. news sites chose to publish photographs of her
playing table tennis with Balazs over the weekend, but MailOnline has
respected her wishes.

Pippa, who turns 29 today, is in town for meetings over her new
book, which is out on October 30. She will not be holding an publicity
events for the book while she is here, Viking publishers said.

Billed as a 'comprehensive seasonal guide to simple and creative
entertaining', it is a book she hopes will cement her credentials as a
party planner, and industry observers believe it could net her a small
fortune in the process.

It is believed that Pippa is set to make an appearance at New York's Fashion Week, which kicks off on tonight.