In pictures: Discovery Channel marks 25 years

Discovery Channel is celebrating its 25th anniversary and to mark its milestone it has released a series of stills showing off some of its most memorable programmes.

While the US network, which now has channels in more than 200 countries, was first primarily known for its natural history programmes its brief has branched out into high-powered machines, exploration documentaries and macho reality TV shows.

Dan Korn, Discovery's head of programming, takes us through some of the images that have shaped the channel, and talks about the future of the network.

"I think that we've always been known for taking viewers into a new world and doing HMS Ark Royal and being on Ark Royal on her effectively last voyage was quintessentially British and was a great opportunity to meet extraordinary characters," says Mr Korn.

"There's so many of these photos that have a resonance for me," says Mr Korn.

"I look at Stephen Hawking's Universe and it was so fabulous to work with Stephen. Like a lot of people I'd read A Brief History of Time, and it introduced me to cosmology and astrophysics and popularised the whole thing. So meeting him was a real thrill."

Grizzly Man, directed by Werner Herzog, told the story of Timothy Treadwell, a man who spent his summers with bears in Alaska. He and his girlfriend, Amie Huguenard, were killed and eaten by a bear in 2003 and the footage was later found. Mr Korn said: "The film is the incredibly powerful and ultimate tale of Timothy Treadwell that he shot himself. That to me is a surprising, unusual and captivating film."

In 2010, British explorer Ed Stafford successfully tackled the Amazon river, having taken 860 days to walk the entire length.

"Walking the Amazon with Ed Stafford was a sort of a unique piece of self-shot footage in which Ed charted his extraordinary journey. He was a great talent, there's always a sense of excitement at discovering new talent," said Mr Korn.

The relationship between Discovery and Ed Stafford has blossomed, with Stafford able to choose his next projects.

"First came Walking the Amazon and then we talked to Ed what he wanted to do next and he said he'd like to do a very pure, what he called an ultimate survival test of being completely naked and dropped on to an island and have to survive entirely on his own for 50 days," said Mr Korn.

This idea became Naked and Marooned.

Discovery Channel's reputation as a network for men with programmes about space, sharks and monster trucks filling its schedule has changed in recent years, as its makes small inroads into gaining a female following.

Mr Korn says: "I commissioned Celebrities Alone in the Wild which had female talent, including freediver Tanya Streeter and Winter Olympian Amy Williams. We've also tried putting a different skew on some of our programming.

"We did suggest when Ed (Stafford) was doing his survival show that we have a woman wash up on the other side of the island but he said: 'No, I can't do that I'm just about to get married!'. At the same time, we were developing Naked and Afraid, (which puts a naked man and woman on an island) and that is something that has co-viewing appeal.

"We are constantly trying to broaden our audience and co-viewing, of course there is a male skew, that's the territory we are into but we want to get more women into the channel."

Oscar-winning director James Cameron has worked with Discovery on a number of occasions, notably investigating the wreck of the Titanic at the same time as his hit film was being watched by millions at the cinema.

Mr Korn says: "At the time it was made, Titanic was the biggest grossing film of all time and, via Discovery, James Cameron went back to the wreck and explored the last relics, last artefacts and the last mysteries of the ship. It was an incredibly atmospheric film, incredibly entertaining, and he is incredibly charismatic."

One of Dan Korn's favourites programmes during his time at the network has been the live event Skywire Live, which saw Nik Wallenda attempt to cross the Grand Canyon.

"For just sheer breathtaking scale, something only a broadcaster like Discovery can do, is Skywire Live, 1,500 ft up, no safety net on the wire for over 20 minutes," he says. "I remember staying up and watching it at two in the morning and thinking, 'This is a true televisual moment'.

"The interesting thing is that Nik comes from a family of highwire walkers and circus performers. His grandfather died falling from a wire in South America. And Nik has been doing it since he was a kid. He wanted to be the (stunt bike rider) Evil Kneaval of skywire walking, something truly memorable."

Nik Wallenda will next attempt a tightrope walk across the skyline of Chicago's skyscrapers for a live event on 2 November.

As Discovery look back at the past 25 years, its executives are also looking to the future and how it will compete in an increasingly over-crowded digital market.

Mr Korn says: "The founder of Discovery, John Hendricks, had a vision for Discovery of satisfying curiosity, which I think has metamorphosed into 'intelligent entertainment'. First and foremost the viewers wants to be entertained but they want it to be nutritious entertainment. They want to have a fantastic story but they want the information."