The BBC's Bleak House was filmed in HD

A total of 450 people are due to collect set top boxes this week for the six-month long technical trial.

It will give the BBC, ITV, Channel 4 and Five a clearer picture about delivering HDTV broadcasts to viewers who watch TV through an aerial.

HDTV broadcasts and set-top boxes are already available to Sky satellite and Telewest cable subscribers.

Sharper image

The BBC's HDTV programming will include the BBC's World Cup football coverage, major Wimbledon matches and programming highlights such as Planet Earth and Bleak House.

ITV will offer its own World Cup coverage in HDTV, as well as drama such as Poirot specials Death on the Nile and Murder in Mesopotamia, documentaries such as Jean-Michel Cousteau's Ocean Adventures and classic films including All Quiet on the Western Front and The Big Sleep.

Channel 4 will contribute US series such as Desperate Housewives and movies from FilmFour, while Five's output will include police drama CSI.

The BBC's programmes are already available to cable and satellite viewers, while ITV's are being carried on cable.

If the trial is successful, it could pave the way for HDTV broadcasts on Freeview.

Viewers need suitable TVs and set-top boxes to be able to pick up high-definition television.

It provides a sharper, clearer and more colourful image than the current standard television picture.