They would like to speak to anyone who was in the Wetherspoons pub at around 3.45pm on Saturday 19 May 2012 and who may have information about the incident. The pub was busy at the time with people who may have travelled to the Thirsk area to attend the races.
The 45-year old man from the Langley area of County Durham, sustained serious head injuries requiring the Yorkshire Ambulance Service to attend. The man remains in James Cook Hospital in Middlesbrough where he is in a critical but stable condition.
Officers want anyone who was in the pub at the time of the incident to contact them if they have not already done so.
Anyone with information is asked to call North Yorkshire Police on 101, select option 2 and ask for Sergeant Simon Hepburn.