Allan, currently deputy managing director of OMD UK, will report to Williams and take up his new position as of January 1, assuming full responsibility for the agency's operations in the UK.
He joined the company in 1995 as part of the agency's graduate recruitment programme, starting his career in media as a TV buyer, moving into planning, then taking the position of a business director at the agency in 2001. He was promoted to head of business management and deputy managing director in 2005.
Williams said: "I've worked closely with Jonathan for all of his time at OMD UK, and I am thrilled that he has steamed through in this succession programme. He is a top bloke, is very bright and has bundles of energy -- the perfect attributes for a managing director.
"His influence in our business and with our clients over the last couple of years has been exceptional. OMD UK is in a really good place right now, with brilliant people producing great work."
The move tops off a successful year for the OMD UK Group, with OMD picking up the £30m pan-European brief for soya drink Alpro and sister agency Manning Gottlieb OMD picking up the £15.5m media planning and buying account for John Lewis stores, following on from the £9m Waitrose media account. The agency also took the consolidated account for NTL/Telewest.
Allan added: "OMD UK, our clients and the fantastic people that we have here have been a huge part of my life since I was 21, so naturally I am delighted to be given the opportunity to lead the agency at such an exciting time in our development.
"I am relishing the prospect of building upon Steve's leadership, driving continuous innovation and new thinking through the business, to make sure we are doing the very best work for our clients and are a few steps ahead of our competition."
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