By William Gallagher BBC News

Emma Thompson is one of the show's celestial stars

It was touted as an all-star epic and for once the claims are completely true.

Angels in America is a six-hour television drama starring Al Pacino, Meryl Streep and Emma Thompson.

"I accepted immediately," Emma Thompson says, adding that she did so because it was being directed by Mike Nichols.

Angels in America counterpoints the heady days of 1980s America with the onset of Aids as it follows a series of characters grappling with the illness or the impact of it on themselves and their friends and family.

Originally a prize-winning stage play, Tony Kushner's story seemed to be obviously destined for the silver screen.

Kushner worked on such a version with directors such as Robert Altman, so you would expect that making it for television might seem a comedown.

Faithful

But Kushner says Altman wanted to change the play and make it in the improvisational style of his previous films, whereas the final television one made by Mike Nichols for America's HBO is much more faithful.

HBO - it stands for Home Box Office - is an unusual American network because it is a cable channel paid for by subscription more than advertising, so people who get to see it have specifically chosen to and have paid money for the privilege.

Read about the show's Emmys success

There are many subscription channels in the UK but they are filled primarily with repeats or low-cost factual programmes.

HBO invests its money in short runs of expensive, critically-acclaimed dramas such as Six Feet Under and The Sopranos.

The subscription model also means that HBO has none of the family viewing concerns that free-to-air American networks have so it can be harsher, more profane - if it wants to - and arguably it can deal with more adult fare.

Meaning

This is what attracted actors such as Meryl Streep.

"We don't ask enough of this film and TV audience; they're hungry for stuff of size and meaning," she says.

HBO's budget for Angels in America was well above the television norm, but not considerably.

Angels cost $65m (�35m) which works out at $10.8m (�5.8m) per hour; The West Wing, admittedly the most expensive hour drama series in America, costs around $6m (�3.3m) per episode.

So it is not money that draws actors in, it is the project itself.

Emma Thompson signed up because she'd just worked with director Mike Nichols on HBO's Wit, but she adds: "Then I read the script. It was incendiary. The first page practically burst into flames in my hands."