By Fergus Walsh
BBC News medical correspondent
My four-year-old son was confused.
"It's you Daddy" he said...."No, it's not, yes it is".
No wonder. I had just shown him a photograph which had the morphed image of another man's face onto my bone structure.
How was it done? Well, it involved a laser scanner, an old squeaky chair and a talented team at University College London and the Royal Free Hospital.
First the squeaky chair. I had to sit very still on it in a darkened room just off Gower Street.
This is where the hospital scans the faces of patients with facial disfigurements.
The chair does a 360 degree turn and as it does so a laser builds up a 3D image of the face. This is transferred to computer.
The result is a grey 3D image which reminds me of those centuries-old death masks you may have seen - Nelson springs to mind.
We weren't doing this for fun - there was a real scientific aim here.
That was to find out what you might end up looking like having someone else's face transplanted onto your own.
The original Fergus Walsh
Would you end up looking like the donor? Would the donor's family need to worry about seeing someone else walking around with the face of their bereaved relative?
Isabelle Dinior has helped to answer some of those questions.
She is the French woman who received the first face transplant in November 2005.
Three months later she faced the world's media to show that her new face was working, and it did not make her look like her donor.
But Dinior only had a partial face transplant.
In Britain the surgeon Dr Peter Butler wants to go further.
He aims to transplant the entire skin envelope of the face, right up to the hairline.
Isabelle Dinior's remarkable operation involved about half that area.
Dr Butler is a surgeon at the Royal Free Hospital in north London and he now has ethical approval to select a patient.
He is part of a large and experienced team which includes Dr Alex Clarke, a psychologist.
To get an idea how a face transplant might change someone's appearance both Dr Butler and Dr Clarke had their heads scanned.
The original Peter Butler
His face was "transplanted" onto hers and vice versa. Neither assumed the other's identity.
The trouble was that with his face, Dr Clarke ended up looking rather masculine. And with her face, Dr Butler ended up looking a little too feminine.
Of course, a face transplant would never be done between the sexes.
So this time I had my face scanned and we opted to have the surgeon's face draped over my bone structure.
A new person
The result was remarkable. Unlike the morphed images of the surgeon and psychologist, this hybrid face really did look like a real person. A distinct personality.
Interestingly, it looked more like me than Peter Butler.
It shows that the shape of everyone's face comes largely from their underlying bone structure.
I can't say I'm comfortable looking at my new face.
The photograph has my hair and my eyes, but it's rather weird. I hope I never meet this person - in a dark alley or anywhere else.