The duo have been a freelance creative team for the past two years and have worked with a number of London-based advertising agencies.
They worked at Bartle Bogle Hegarty London between 2007 and 2009 on brands including Audi, British Airways and Johnnie Walker.
Before BBH London, the pair had stints at Rainey Kelly Campbell Roalfe/Y&R and VCCP, where they worked on Marks & Spencer, Virgin Atlantic, Coca-Cola and O2.
Russell Ramsey, the executive creative director at JWT London, said: "Bill and Giles have done some great work on some very grown-up brands. I'm delighted they’re joining JWT."
The appointments follow that of Jeremy Carr and Dave Masterman, who were named creative directors at JWT last year.
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