Amazon has opened a till-less grocery store in London.

Visitors to Amazon Fresh in Ealing scan a smartphone app when entering and are automatically billed as they leave.

The store stocks hundreds of own-brand items as well as third-party products, and also serves as a place to collect and return goods bought online.

Amazon said the Just Walk Out technology uses "computer vision, deep learning algorithms, and sensor fusion".

Matt Birch, the former Sainsbury's executive who now leads Amazon Fresh Stores UK, said the company has tried to make grocery shopping "as convenient as possible".

This Is Local London: Visitors can buy a bag or use their own, and are emailed a copy of their receipt after leavingVisitors can buy a bag or use their own, and are emailed a copy of their receipt after leaving

"The focus was just creating a really easy shopping experience for customers," he said.

"We recognise that UK customers want to shop in a convenient way so we really think they will appreciate being able to walk in and walk out with the shopping they need."

Campaigners have raised privacy concerns but one retail expert said the opening marked a "watershed moment".

"Having a physical presence will enable Amazon to address some of its weaknesses, like the mounting cost of deliveries and returns," said Natalie Berg, an analyst with NBK Retail.

But she said she did not believe it would pose a threat to the major chains in the near term.

"Supermarkets have had a few years now to prepare and test their own checkout-free shopping concepts."

Amazon's approach, however, promises a more "frictionless" experience than other retailers.

Visitors only have to place an item in a bag or otherwise carry it out to be charged by the store, which is located at the street entrance of a shopping centre in the borough of Ealing.

By contrast, retailers including Marks and Spencer, Tesco and Sainsbury's require consumers to scan items into a smartphone or other device.

The company is so confident of its tech that it says shoppers are not under any obligation to check all the items were accounted for.

"When you're finished, you're free to walk out," added Matt Birch.

Amazon, the world's largest online retailer, has yet to dominate the grocery category but its expansion beyond the US is a sign of its intention.

In the US, it acquired the Whole Foods Market chain in 2017 and has around two dozen Amazon Go stores, which are cashierless convenience stores.

It also has two Amazon Go Grocery stores, which are larger, and 10 Amazon Fresh supermarkets in California and Illinois.

The company said it is looking forward to opening more stores in the Greater London area.

In July last year, Amazon launched a grocery delivery service for Amazon Prime customers in or around London.