This is what we found on Wikipedia regarding the York Barbican Premium Seating:

ATG Entertainment, formerly The Ambassador Theatre Group (ATG), is a major international live entertainment organisation headquartered in the United Kingdom, with offices in Woking (head office), London, New York, San Francisco, San Antonio, Madrid, Mannheim and Cologne. ATG's key operations comprise three inter-related activities: venue ownership and management, ticketing and marketing operations, and show productions.

ATG runs more than 64 venues in Britain, the US and Germany. The company is among the most prolific theatre producers in the world with co-productions in the UK, New York, across North America, Europe, Asia and Australia. It is involved in event ticketing services through ATG Tickets, LOVEtheatre and Group Line.

The company was founded and run by the husband-and-wife team of Sir Howard Panter and Dame Rosemary Squire OBE, who topped The Stage 100 list of prominent UK theatre personalities from 2010 to 2016.