BritBox, ITV and the BBC’s joint “best of British” streaming service, is not being positioned as a rival to Netflix and Amazon but offers something those two streaming giants don’t, ITV director of television Kevin Lygo said.

Speaking at the Edinburgh TV Festival on Friday, Lygo said BritBox would be a “different thing” that allowed ITV and the BBC, Britain’s two biggest broadcasters, to put their extensive back-catalog to best use. The service already operates in North America, where it has 500,000 subscribers, and is set to launch on home turf in the U.K. in the last three months of this year, with a large collection of British boxsets and some original series, such as detective drama “Dark Heart.”

“It is not a rival to Netflix and Amazon, who spend billions and billions. This is a way to use the archive of the BBC and ITV,” Lygo said.

“British people are mostly interested in British programming,” he added. “Although Netflix and Amazon are wonderful things, they don’t do a lot of British programming at all. They say they will, but I haven’t seen anything yet that is great” – despite the critical and popular success of Netflix’s “The Crown.”

Lygo said that BritBox was about ITV “looking for a new revenue stream that doesn’t cannibalize advertising revenue.” The broadcaster has sought to diversify its business in recent years away from reliance on advertising, notably by building up its production division, ITV Studios. Lygo made it clear that BritBox fits into this pattern of diversification.

“Everyone knows advertising is a challenge and has an uncertain future, even though they have been saying that as long as I have been in telly,” he said. “BritBox is about subscription television.”

Lygo also insisted that overnight ratings remained an important barometer for judging the success of a show on terrestrial television. “An extraordinary amount of TV that is viewed is still live and from terrestrial,” he said, adding: “Only people who are not getting good overnights say they are not important. Even if they’re going down, they are still a really good indication of how popular a program is.”