Portman Travel, one of the UK's biggest independent travel management companies, has bought rival agency P&O Travel.
Portman, which has offices in London and Glasgow, said the acquisition would increase its size by 30% and make it the largest independent in Britain.
The fee Portman paid to P&O's owner Carnival plc has not been revealed. Portman had a turnover of £200m in 2005 while P&O's was around £60m.
The buy up is the latest in the business travel industry which has seen a series of major consolidations throughout the year.
This is the fourth acquisition Portman has made in recent years, having previously taken over AA Business Travel, John Cory and Travelforce.
Both Portman and P&O, which has four offices in the UK, are shareholders in Radius Travel, a global network of TMCs.
Graham Flack, Portman's ceo, said the two companies knew each other because of the links to Radius and both provided service via local teams.
He added: "Increasingly customers are demanding both the cost-effectiveness that comes with scale and the high levels of customer service and flexibility associated with independents.
"This acquisition is part of our continuing strategy to combine the highest levels of efficiency with the highest standards of customer service."
Eurostar stakes "green" credentials
Flights between London and Paris and London and Brussels generate ten times more carbon emissions than train trips, Eurostar said.
Research commissioned by the high speed train service between London and the continent found that a return flight between Heathrow and Charles de Gaulle generated 122kg of CO2, compared with 11kg for a traveller on a London-Paris return train journey.
For a London-Brussels trip, the emissions were 160kg of CO2 for the plane and 18kg for the train.
Eurostar said the research, carried out by Paul Watkiss Associates and AEA Technology Environment was the most detailed ever produced.
It used detailed data on electricity supplies, power station emissions and transmission losses, Eurostar and airline load factors and the range of aircraft and engine types and emissions.
Of the 1,019 British travellers questioned in a separate poll by market research company YouGov, 41% said they were "much more likely" to take the train than the plane
About the same number, 39%, said they had changed their travel habits in some way because of worries about climate change, including 3% who had stopped flying and 6% who had reduced the amount they fly.
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