Mobile phone network operator EE has launched what it is calling the UK's lowest-priced smartphone - costing just £39 for existing customers or £49 for new customers. The Rook, available immediately, is aimed at the 2.5 million customers who are currently priced out of the superfast 4G service. It runs the Android 5.1 Lollipop operating system, contains a 5-megapixel camera, and has 8GB of internal memory - which can be expanded to 32GB - as well as a battery that promises over five hours of talk time and over 400 hours stand-by-time on a single charge. Access to 4GSharon Meadows, director of devices at EE, said: "Everyone should have access to 4G and the experiences it offers on the go. The Rook provides a great 4G smartphone at a compelling price – allowing even more people to enjoy the benefits of our superfast mobile network from high speed web browsing and downloads to gaming and streaming." The Rook is available on pay as you go, though customers must spend £10 on a top-up when they first purchase the device, while customers who purchase a Rook will also benefit from up to a 20% discount on some EE accessories. Rob Kerr, mobiles expert at uSwitch.com, said the Rook offers superfast data speeds at a compelling price but warned that customers would be locked to the EE network. "4G phones under £50 aren't exactly littering the ground, so this is a compelling offer for those of us on tight budgets," he said. "If you're only planning to spend £50 on a smartphone, it's unlikely 4G is high on your priority list, but there will be people who want fast mobile internet on a shoestring, and The Rook certainly fits the bill. "In terms of specs, The Rook has solid, entry-level features including a fast processor, the latest Android 5.1 and all-important 4G, so this is a good bet for EE pay as you go customers who want the 4G experience for less. "But beware that the handset will be locked to the EE network, so you'll need to fork out an unlocking fee if you want to use it on other networks."