The deal, struck for an undisclosed sum, will make Browns "the world's leading tea exporter", a joint statement read. It will also be one of the largest suppliers to Lipton.

The closure of the transaction, which includes the Kericho plantation in Kenya that has been at the centre of historical violence and human-rights issues, is subject to regulatory approval.

All tea sold by Browns – which, after the deal, is set to export around 87,000 tonnes a year – will be "grown and harvested to a new set of standards covering quality, social and environmental protections". Further details were not disclosed.

A tranche of shares equating to around 15% of the main Kenyan operating company will be offered to communities in Kericho and Bomet, where the estates are located.

Brown will also invest in its estates in Kenya and Sri Lanka to meet the new standards by 2025. The investment will include the modernisation of factories in the country, crop diversification, and support of biodiversity.

Natalia Roos, Lipton Teas and Infusions' CEO, said: “Browns is the perfect partner, with the credibility, capabilities and scale to work with us to raise standards in the whole tea industry. The team’s commitment to sustainability and community development aligns with our own.”

Kamantha Amarasekera, chief executive director at Browns Investment, added: “This partnership marks a significant step towards elevating the industry as a whole, while also ensuring a positive impact on the livelihoods of the communities we serve.”

The two companies are also jointly creating a Community Welfare Trust with Ks1bn ($7.6m) “dedicated to helping address the needs of local and neighbouring communities”.

Lipton Teas and Infusions is the former Unilever tea and herbal drinks business, known as Ekaterra when private-equity firm CVC Capital Partners acquired the assets from the FMCG group three years ago.