The pair met at DDB in 2002 but have never worked as a team before. They will oversee a range of clients and report to Dave Henderson and Richard Denney, the joint executive creative directors.
During her time at DDB, Casey created the D&AD Award-winning "fashion victims" for Harvey Nichols and a spot for The Guardian. She has also worked at Bartle Bogle Hegarty and Rainey Kelly Campbell Roalfe/Y&R on British Airways, the BBC and Oxfam.
Silburn has previously worked at Lowe and Fallon Minneapolis, and has won a D&AD Pencil and Cannes Lions for work on Stella Artois. She also produced the "royal wedding" online film for T-Mobile, which was the UK’s most-watched ad on YouTube in 2011.
Henderson said: "They have an incredible appetite for work, an infectious enthusiasm and a proven ability to write the hits. Rich and I are very pleased they want to make this their home."
In January, Havas Worldwide London poached DLKW Lowe’s Andy McAnaney, Christian Sewell and Jamie Craven.