Carol Slater, a London violinist, had her 1700 Gofriller, in a dark red case, taken from a Gatwick Express train at 0630 last Friday.
British Transport Police today issued this picture of a woman they want to interview in connection with the theft.
They have also issued this image of the stolen violin.
Anyone with information, please call the police on 0800 40 50 40 or text 61016, quoting ref. no. 116 24/03/2017.