YouView, a new set-top box offering subscription-free digital and catch-up TV, has launched in the UK.
The venture, which had been due two years ago, was unveiled by chairman Lord Sugar and CEO Richard Halton at the London Film Museum.
Lord Sugar described it as a "great moment in British television", while Mr Halton said the service "seamlessly combines the worlds of catch-up and live TV, on the living room TV".
YouView offers more than 100 digital TV and radio channels, seven day catch-up and on-demand programmes from the BBC, ITV, Channel 4 and Channel 5.
The set-top box means viewers can see or hear the content on their TV instead of having to use a PC, laptop or tablet.
YouView features an electronic programme guide that lets users scroll back seven days to catch up on programmes they have missed.
Viewers can watch programmes in HD, and they can record, pause and rewind live TV.
The set-top box can be plugged into either a broadband internet connection or a television aerial.
Marc Chacksfield, deputy editor of the technology news website TechRadar.com, said: "Given that YouView was originally meant to come out in 2010, the service has been subject to many delays.
"So, what we are seeing today isn't quite as revolutionary as its makers would like us think."
But he went on: "YouView offers a near seamless experience of on-demand and live TV, but ... the only thing new here is ease of use.
"You get all this content from one electronic programme guide and don't have to flick between a load of different service.
"While this is great, at £299 the boxes are expensive and there are just four on-demand options available at the moment.
"The box won't really come to life until other content providers come on board and that's what Sky will be doing later in the year."
The STBs are expected to be available in the shops by the end of the month, or can be obtained from an internet service provider as part of a phone and broadband package.
YouView said it would soon include more content from the likes of Sky's Now TV and STV.