BT has agreed a deal to buy mobile service provider EE for £12.5 billion.
The telecoms giant will take over EE, a network operator that offers the 3G and 4G connectivity BT has long-coveted as it looks to introduce quad-play broadband deals.
EE, which has 24.5 million direct mobile customers, currently has the largest super-fast 4G subscriber base of any network operator in Europe.
The company - which was formed in 2010 through a merger of Deutsche Telekom and Orange's UK mobile businesses - is expected to join the BT Group by March 2015.
BT said the combination of EE and its own business will provide customers with "innovative, seamless services" that combine the power of fibre broadband with Wi-Fi and advanced mobile.
"Integrating the two companies will accelerate BT’s mobility strategy and increase [its] capacity for future investment and product innovation as it continues to build world-class digital infrastructure in the UK," the firm stated.
BT is to pay for EE with a combination of cash and BT ordinary shares. Deutsche Telekom will take a 12 per cent stake in BT and be entitled to appoint one non-executive member to the BT board, while Orange will hold a four per cent stake in the expanded company.
BT Chief Executive Gavin Patterson said the deal represents "a major milestone" for BT, as it will allow the firm to accelerate its mobility plans.
"The UK’s leading 4G network will now dovetail with the UK’s biggest fibre network, helping to create the leading converged communications provider in the UK," he claimed.
"Consumers and businesses will benefit from new products and services as well as from increased investment and innovation."
EE Chief Executive Olaf Swantee said that joining BT represents "an exciting next stage" for the company, its customers and people.
He claimed that, over the past four years, EE has built the UK’s "biggest, fastest and best" 4G network, significantly advancing the digital communications infrastructure for people and businesses across Britain.
Mr Swantee added that the deal will ensure the UK remains "at the forefront of the mobile revolution", bringing even more innovation and investment in world-leading connectivity for its customers.