The agency was appointed on Friday after a three-month pitch process, which began in January. In February it listed the six agencies that took part in the review, which did not include incumbent agency Abbott Mead Vickers BBDO.
Stephen Robertson, interim marketing director at WH Smith, said: "We are delighted to be able to appoint Delaney Lund Knox Warren, following an impressive pitch process. Our final decision was based on a combination of the excellent standard of strategy and ideas, as well as a cultural fit with the team at WH Smith, which we felt was vital to ensure the delivery of a successful advertising campaign in the future."
AMV declined to pitch take part in the review after it held the business for eight years, during which time it produced the series of ads starring the 'Only Fools and Horses' actor Nicholas Lyndhurst.
Greg Delaney, chairman at DLKW, said: "We are delighted to be working with a British high street icon like WH Smith."
DLKW will take over the account in June and will work alongside Carat, which was appointed to the retailer's media planning and buying account earlier this month.
The appointment of Carat brought to an end another long relationship -- Starcom Motive had held the books and stationery group's media for 10 years.
MediaCom, Universal McCann and Walker Media also took part in the media pitch, which was overseen by the brand communications director Katie Spriggs and assisted by Billetts.
The DLKW appointment comes as the future of WH Smith is in doubt following a long history of poor trading, with a string of profit warnings, as competition from supermarkets on its core books, games and DVD markets bites.
As part of its revival strategy, WH Smith is axing hundreds of jobs following the appointment of former Argos managing director Kate Swann as chief executive. She replaced Richard Handover, who became chairman.
A number of bidders have emerged for WH Smith including private equity firms Cinven, Apax Partners and CVC. Tim Waterstone, the entrepreneur and founder of the book chain that bears his name, said he was also considering a bid.
Reports suggest that bids for the group, the main business of which is stationery and books, could reach as much as £1bn.
It could also see the retailer's publishing arm, Hodder Headline, and news distribution arm sold off.
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