Hytner has worked in the television industry for the past decade and was responsible for introducing a cleaner, more coherent on-air look for the ITV channels.
However, the Barclays job is considered one of the biggest in the business and puts him in charge of a marketing budget that, at around £350 million, is more than 100 times bigger than that at ITV. He replaces Simon Gulliford, who quit last month.
The company has appointed Bird & Co to find Hytner's successor. His departure comes as ITV finds itself once again under City pressure because of its declining audiences.
Hytner joined ITV in 2001. In 2003, he persuaded the shareholders of the premerged company to drop their regional logos in favour of a single ITV-branded one, created by Bruce Dunlop & Associates.
Hytner introduced new break bumpers, break flashes and end-credit promotions detailing the rest of the night's viewing on ITV channels in an effort to keep viewers watching. He also persuaded celebrities from ITV programmes to appear in ITV's promotional break bumpers.
However, since the on-air changes and amid increasing pressure on costs at the network, ITV has dramatically cut its marketing budget. Spend has been as low as £3 million, less than the amount available at any of the other main broadcasters.
The appointment of Justin Sampson at ITV Sales as the director of customer relationship marketing also took away some of Hytner's responsibilities.