The Brit studied the beloved nun's movements and mannerisms as she prepared to portray her and she was stunned when Indians believed she really was their heroine reincarnated.

"We shot quite a lot in the slum settlement on the edge of this town in India for weeks and weeks," Stevenson tells WENN. "There was one morning where I was waiting to shoot and I was wearing the sari with the iconic blue stripe over the forehead. I felt something at the bottom of my robe and I looked down and there was a man, a passerby, who just dropped to his feet and was touching the bottom of my sari.

"Then he got up and just walked off. I said to somebody, 'Well, what's that all about?' They said, 'He's touching the hem of your garment because he thinks you're Mother Teresa'. I said, 'That's crazy. Here's the film crew, and everybody knows she's dead'. They said, 'Yeah, but for him she's not dead'.

"That happened a few times and it was wonderful for me that it did happen because here we are in a strange place where fiction and life are overlapping; the division between the two had disappeared. And in India she's still a hugely revered and loved figure. It was extraordinary there. Some people would just stare at me from a long way away as if they couldn't quite believe it."

The actress worked hard to capture Mother Teresa's famous stoop and her gentle nature, insisting her body language "tells her complicated story".

"She was so hunched with her shoulders kind of hunched up around her neck with this concave chest," she explains. "I had to make my neck look shorter and my shoulders hunched up and that little face always looking up because she's always the smallest person in the room.

"Once you get that iconic shape I could believe I was her. It's a bit like being a painter. I was very determined to get it right, so sometimes I would look at myself on video playback and I needed to hunch that shoulder even further up near my ear! I did get quite sore and quite bent. I did get into some posture difficulties.

"I had an aching sore and stiff neck because she was quite tense in her body but her hands would be completely relaxed with this touching. I did have to go and have massages which fortunately are cheap in India."