"John's Key's Facebook pic is very interesting as Bill English is positioned a lot higher than John Key, which in body language terms puts him in the higher status position, as does his very upright posture," said Suzanne Masefield of The Body Language Company.
But she said Mr English's hands were held in tight fists on his lap, which suggested "either stress, anxiety or controlled anger".
Ms Masefield said John Key's lowered position, leaning in with his left arm in an "exaggerated stretch" towards Mr English, suggested he was very comfortable and wanted to show his connection with him.
She said the picture also suggested the Prime Minister was "deferring" to English's status, "possibly around the Budget if this picture has just been posted."
In other words, Ms Masefield said Mr Key was sending a message that he trusted Mr English and got on well with him.
"And whilst he's the ultimate boss, in this instance he defers to Bill English's expertise, and his positioning suggests he's passing the power over to Mr English."
It wasn't yet clear if the photo was staged.
"Whether this is a natural pose or one created strategically for the camera is uncertain, so the picture needs to be taken in context," Ms Masefield said.
