It comes just 24 hours after Blackpool businessman and founder of the Fylde travel firm scooped a £47m payday from the deal.
Ken Townsley, who set up Gold Medal, sold a 50.01 per cent majority stake in the business just over a year ago.
The Thomas Cook Group plc has now completed the acquisition of 49.9 per cent of the firm in a £24.9m deal.
Gold Medal – which also owns Leeds United sponsor netflights and the upmarket Pure Luxury tour operator – specialises in holidays to the US, the Far East and Australasia, as well as holding a market leading position in Dubai.
Mr Townsley, a former baggage handler at Blackpool airport, has earned more than £72m from the sale of the business, which has 540 staff.
Gold Medal takes around 600,000 travellers to 1,500 destinations every year and made pre-tax profits of £8.1m, with sales of £309.7m in the year to September 30.
Manny Fontenla-Novoa, group chief executive of the Thomas Cook Group, said: "Since we acquired a majority stake in the business a year ago, the travel company has traded exceptionally well, clearly demonstrating the strategic importance of having a strong presence in this market. We are confident the business will continue its strong growth and generate synergies within the Thomas Cook Group.
"The agreement to acquire the remaining stake in Gold Medal Travel underlines our commitment to further strengthening our position in the growing independent travel sector."
Thomas Cook had an option to buy the rest of the business by March next year.
Last December, Mr Townsley sold a majority stake in Gold Medal to Thomas Cook, almost 40 years after establishing the company from a small office on Church Street in Blackpool.
The deal made Gold Medal the UK's fourth largest tourist operator. It has flown more than 400,000 passengers on holiday this year alone.
Gold Medal Travel moved from its Blackpool base a few years ago to a new home on
Preston Docklands.
It employs more than 500
people, many of whom have been with the company since it was on the Fylde.