Who's in and who's out as Aussie socialites take over London's most exclusive party - as elites whisper about the two notable names missing

The Serpentine Summer Party has long been regarded as having one of the most ruthlessly curated guest lists on the British social calendar.

Held at the Serpentine Galleries in , the annual event is known for its exclusive invitations, typically drawing a mix of celebrities, aristocrats, art patrons, fashion powerbrokers and established old-money social fixtures. 

The event is so tightly controlled that society watchers refer to its exclusive guest list as 'The Serpentine Effect' - a test of who's in, and who's out, of London's high society inner circle. 

For Australian socialites in London for the European summer, that filter is even more brutal. 

Each year, the party becomes an unofficial audit of which Australians have successfully embedded themselves within Britain's elite cultural and social networks - and which remain on the periphery.

This year, only a small number were able to break through.

The most well-known Australian to attend was, of course, Isla Fisher, who posed on the red carpet in a stunning pink gown by Aussie designer Rebecca Valance.  

Olivia is the wife of investment manager Jeremy Bond, grandson of the late Alan Bond, and her invitation certainly proves that established family lineage and financial pedigree carry weight well beyond Australia's borders. 

Interior designer Tamsin Johnson, the wife of fashion entrepreneur Patrick Johnson, also scored an invitation.

So did the well-connected charity maven Francesca Duncan.

Francesca is, of course, the wife of Campbell Duncan, whose father is coal-mining magnate and Rich Lister Travers Duncan. Her sister-in-law is the powerful corporate lawyer Andromeda Neale.

Olivia, Tamsin and Francesca made their presence known, sharing photos of themselves dressed to the nines as they posed for photos at the event.

The Serpentine Effect had two Australian casualties, however.