Holberton is charged with handling UK and European corporate affairs for the firm, which is listed on the Australian Stock Exchange and is the world's largest retail property group by equity market capitalisation.
He joins after three years' working on Brunswick's account with Westfield. He also advised on other property and luxury goods briefs.
Before joining Brunswick, Holberton worked for the Financial Times, covering global capital markets while living in Hong Kong and mainland China.
As well as the White City project, Westfield owns major shopping centres in Nottingham, the West Midlands and Guildford.
The company hit the headlines last month when fellow Australian firm Multiplex sold its role in the £1.5bn White City project to its rival. The deal, which cost Westfield £20m, is likely to see it retain many of the Multiplex staff already on site.
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Separately, retail specialist comms agency Primal PR has just won a three-year contract to promote Henderson Global Investors and Insight Investment's £250m redevelopment of Hull's Princes Quay shopping centre.