Officers have released an image of a man they want to speak to in connection with fraud.
An Elstree based firm received an e-mail in January, believed to be from a supplier, notifying them they had changed their bank account details.
But when the company made payments into the new account, the supplier called them to say they were behind with payments.
When the new account was queried, the supplier confirmed that no change of account had taken place.
The brown-eyed man is believed to be from the Hounslow area and may hold information that is vital to the investigation.
DC Damien Hewitt, from the local crime unit in Borehamwood, said: “If this is you or you recognise this man please get in touch with Hertfordshire police as soon as possible.”