(Reuters) - GlaxoSmithKline Plc GSK.L Chairman Philip Hampton will step down after more than three and a half years in the role, as Britain's biggest drugmaker prepares to split its business into two.

The GlaxoSmithKline (GSK) logo is seen on top of GSK Asia House in Singapore, March 21, 2018. REUTERS/Loriene Perera

The announcement comes a month after GSK’s Chief Executive Emma Walmsley announced her boldest plans yet - to split the company into two businesses -- one for prescription drugs and vaccines, the other for over-the-counter products.

Walmsley, who took the helm in 2017, announced in December that GSK and Pfizer PFE.N would combine their consumer health businesses in a joint venture with sales of 9.8 billion pounds ($12.7 billion), 68 percent-owned by the British company, in an all-equity transaction.

“Following the announcement of our deal with Pfizer and the intended separation of the new consumer business, I believe this is the right moment to step down and allow a new Chair to oversee this process through to its conclusion over the next few years,” Hampton said in a statement.

Hampton, aged 65, was paid a sum of 700,000 pounds ($900,550), of which he elected to take 25 percent in GSK shares, according to the company’s 2017 annual report.

He took the top job at GSK at a testing time - just after a profit warning in 2014 due to weak sales of its core respiratory drugs.

The Briton was tasked with helping steer the drugmaker back to sustainable growth. Shares of GSK have, however, remained flat after peaking about 17 percent during his tenure.

They were little changed in early trading on Monday.

GSK, whose consumer products include Sensodyne toothpaste and Panadol painkillers, has lagged rivals in recent years in producing multibillion-dollar blockbusters and it largely sat out a spate of dealmaking by rivals under previous CEO Andrew Witty.

Seeking to reassure investors of its financial strength, GSK extended its guarantee on the dividend by stating it expected to pay unchanged dividends of 80 pence per share for 2019.

Before joining GSK, Hampton was chairman of Royal Bank of Scotland Group Plc RBS.L and J Sainsbury plc SBRY.L.

He was parachuted in to help rescue RBS following its 45 billion pounds bailout during the financial crisis and led the bank through a turbulent period of transition.

GSK, which has been looking to buy early-stage assets and partner with companies, said it had started the search for a successor.