Amazon is hiring an additional 400 employees for a new research and development centre focused on machine learning in the UK. Currently, the company has about 20,000 people in the country.

The Amazon Cambridge Development Center is looking for scientists for the development of advanced hardware such as Echo speaker and Prime Air drones.

In 2016, the UK business generated revenues of $9.55bn (£7.40bn), up 21% on a year earlier.

"The UK has been an incredibly important business for us. We [are] concentrating scientific development work in London, Cambridge and Edinburgh, because they attract great people ... the UK is such a great place to recruit machine learning expertise,"Jeff Wilke, Amazon chief executive of worldwide consumer retail, told the Financial Times, in an interview.

"For us, it's a place we will continue to invest in heavily for all of those reasons," Wilke added.

The company has plans to add another 5,000 UK workers, launch a 600,000sq ft headquarters in central London and operate three new fulfilment centres across the country.

"Programmes like the Echo/Alexa, the whole Fire TV series, Kindle, Prime Air, all of that has happened inside the UK and we expect to see more of it," Wilke told the FT.

Amazon has made a deal with the Civil Aviation Authority (CAA) in the UK to operate multiple drones in the area.

In June 2016, the company launched Amazon Fresh and Pantry to take on services offered by major UK grocers such as Tesco, Asda and J Sainsbury. Amazon Fresh is now available in 266 postcodes in London, with about 40% of Amazon Prime Now members in the UK.

The company has even doubled the items available for UK consumers from 150 million to 250 million unique products, starting from bike parts to clothes, pet foods, beauty products and scientific equipments.

A major challenge for Amazon for its UK business is to ensure capacity of its transport network.To deal with this the company might even use its own branded aircraft.

"We have a great opportunity to enable sellers in the UK to expand their exports [but] we have to make sure we have the transportation capacity to move items from UK warehouses to the countries we are shipping to. That means ... making sure there is enough air capacity ... we may have to employ planes in order to do that effectively," Wilke noted.