Pippa Middleton had a serious look on her face as she headed to work today in London.

Perhaps Pippa was busy thinking about how they would be celebrating her sister Kate Middleton's 30th birthday later in the evening.

OK! GALLERY: PIPPA MIDDLETON HEADS TO HER OFFICE IN LONDON

It has been reported that instead of a big fancy party, Kate's birthday would just be a "low-key and private affair."

Not what you would think for Kate's first birthday celebration as a royal, since she married Prince William in April.

OK! GALLERY: PIPPA MIDDLETON SHOPS AND STROLLS AROUND LONDON

Pippa was, of course, looking as stylish as always in a striped skirt and fitted blazer.

Are you surprised Pippa and the family aren't throwing Kate a big party?