The agency picked up the business after a final shoot-out against McCann Erickson.
The pitch, which was handled by the AAR, was reduced to two agencies after Delaney Lund Knox Warren & Partners and DDB London were knocked out at an earlier stage. The incumbent on the account, St Luke's, declined to pitch for the business.
RKCR's brief is to create an overarching global idea for the company's business-to-business communications, covering sectors including IT and consultancy.
The loss is a blow to St Luke's, which has worked on the account for the past six years. The business-to-business account was its biggest-billing piece of business and accounted for nearly half of its £40m billings.
Last year, St Luke's also lost its BT consumer accounts. Its 118 500 business was rolled into Abbott Mead Vickers BBDO following a pitch for the entire £40m consumer account.
St Luke's remains on the BT roster, however, with a project for BT's Open Reach.
The review is not thought to affect the telecoms giant's roster of media agencies, which includes Starcom on TV, radio and press buying, PHD on media planning, and Zed, which handles online buying.
Neither RKCR nor BT would comment as Campaign went to press.
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