Thanks to Jezi for the most recent purse ID and that is Victoria's lovely Jil Sander Madame Frame bag. This bag is from the spring 2010 line and is a chic navy color. It is lizard skin and has gold hardware.
While browsing the Jil Sander online shop myself, I couldn't find the exact bag (although I did see it in different combinations and materials) Victoria had at LAX and Heathrow, but much to my surprise, I came across yet another purse she has in her enviable and never ending closet. This navy calf leather shoulder bag is the one she was toting back in July when she and David picked up the boys in London after their anniversary vacation in the Seychelles. This bag is available to purchase online here for $1,895.
*Thanks again to Jezi
source: Zimbio & Jil Sander