Ewan McGregor, Jonny Lee Miller, Ewen Bremner and Robert Carlyle have reunited with the Oscar-winning director for the follow-up to the ground-breaking 1996 hit.
Boyle, 60, explained the reasoning behind the new title in an interview on The Chris Evans’ Breakfast show, after the DJ joked “T2 is good but it sounds like a smaller BA terminal”.
The filmmaker said he wanted to call the movie T2, which Terminator 2 is sometimes referred to.
“I always thought that if these characters were asked to do a sequel they would agree reluctantly and say ‘all right but you have got to call it T2 so that you can annoy James Cameron (director of Terminator 2)’.
“Terminator 2 is known as T2 but actually not legally. We can call our film T2.”
But he added: “The reason Trainspotting is added after it is because everyone books online now and online things do take you to the James Cameron film, rather than our film, so we had to concede defeat to commerce eventually.”
Asked if he would do a third film, Boyle said: “I would love to get this lot back together again.”
He said there was a lot more money for the sequel, but the cast were all paid the same as each other.
The first film was shot in Glasgow despite being set in Edinburgh because they could not afford to film in Scotland’s capital.
“We didn’t take as much money as we were offered because we wanted to keep a perspective on it,” he said of the new film.
“We said to the guys, ‘we are going to pay you all the same (as each other) but it won’t be a great deal of money.
“’But if it is a success you’ll all share equally in the profits of the film’.”
Asked about the cast’s feelings about reuniting to make a sequel for such a successful movie, he said: “There was an anxiety...I’d sometimes see them looking at me.
“I could tell what they were thinking, which is this better not be bad.”