Moviemaker Danny Boyle is negotiating deals to bring the original Trainspotting cast back together for a sequel.

The director plans to release the film, Porno, in 2016 to mark the 20th anniversary of his original adaptation of Irvine Welsh's bestseller.

He says, "It won't be an adaptation of the book Porno. What it will be more is an examination of those actors and the same characters 20 years later. It's a wonderful, acute way of looking at these guys and what you can get away with and the risks you can take in your 20s, and then you get in your 40s and the osteoarthritis begins to set in and it's not quite so easy. It'll be classic; them looking at what they've made of their lives in 20 years.

"It'll be cruel yet hopefully very moving. You'll have a double reflex because the characters Begbie (Robert Carlyle) and Spud (Ewen Bremner), which everybody remembers, will be 20 years older and look 20 years older, and the actors will also be 20 years older. So, you'll watch it thinking, 'Wow, where did that 20 years go?'

"We will do everything we can to get the original cast. They haven't signed a deal to do a sequel in the original contract because nobody thought it would live on like this."