We've been working with many of our supplier for decades, and in some cases generations, so it didn't feel right that we'd leave them behind as we moved towards all our teas coming from independently certified farms. The Rainforest Alliance model gave us the flexibility we needed to bring our most trusted suppliers with us.

A great example of this is Doomur Dullung, one of the oldest and best tea producers in Assam. Our relationship with this estate goes back longer than Yorkshire Tea itself so it meant a great deal to us when we got them on-board - some tea producers in India are choosing to stop dealing with Europe and its complex and demanding standards, and focus instead on the fast-growing internal market where doing business is far easier.

Not so for Doomur. The relationship we've built with them is very strong thanks to our shared values, and frequent trips to meet them out there in person. So when we started talking to them about working towards Rainforest Alliance certification in 2009, they were quick to respond.

Our Head of Tea Ian visited Doomur with representatives from Rainforest Alliance to talk through the key principles and the various standards that would need to be met across the board. Because of the work done together over the years, a great deal of the methods and practices were already up to scratch, but this pilot visit helped to identify other ways to improve too - carrying out a training programme to ensure all staff understood the importance of recycling and waste management, and the correct use of fertilisers and agrochemicals. There were also wider environmental points to look into, such as tree planting programmes, and waste water filtering initiatives to protect the local ecosystems.

Throughout the process we were delighted with the positive attitude of our partners at Doomur, and with the support provided by the Rainforest Alliance.

As luck would have it, SK Mitra from Doomur came to visit us this week so we got a chance to ask him for his perspective on working with the Rainforest Alliance. He told us: "The move to Rainforest Alliance all began when Ian came to us about it. Much of what we did already - such as our mother's clubs - put us in a very good position, but everyone at Doomur Dullung saw the benefits of going further straight away, and we quickly went from committing to work on four of our gardens to another five. Internally there was a lot of excitement about it, and it was very satisfying when we received official notification that we'd achieved certification earlier this summer."