The chain plans to open 300 convenience stores over the next 10 years.
Last month, The Grocer revealed Waitrose has been laying out the meat offer in its c-stores by protein groups to help shoppers plan their evening meals. Ranges have also been geared towards shoppers looking for items for the next 24 hours.
"We have learnt a lot to date in terms of what works and what doesn't," said Waitrose head of convenience Jon Arnold. "We take all this into account when opening a new store.
"We are getting better at this but are still very much in our infancy. We are doing this as a trial and are still learning a lot about this market."
There were a lot of retailers with more experience in convenience, he added. However, he said: "We have made no secret of the fact that if we make a success of it, we want to continue to build on that but it is still very early days and we have to be mindful of that."
The retailer has focused on two formats for its convenience offering large and small. At 4,698 sq ft, the Amersham branch follows the larger-format which, in common with the other c-stores already opened, has a bakery at the front of the shop.
"Having the bakery at the front of our stores is very important as it sets the tone for customers' expectations and stands for quality," Arnold said.
Waitrose plans to open another two c-stores in January, both in the London area.