Durham's bid to host the NCS Congress in 2020 was conditional on total numbers (including both
the local organising team) not exceeding 500. This number was set by a number of factors: a) the safety-regulations governing the use of the Teaching and Learning Centre (particularly our use of the top floor for lunch, refreshments and one of the receptions; b.) the maximum capacity of the largest lecture theatre in the TLC; and c.) the maximum capacity of the Cathedral's nave. This is why all of the initial planning was on the basis that the local team would be welcoming no more than 480 delegates to the city.
At the request of the NCS, this number was revisited in January 2020. Since the TLC opened for the first time in October 2019, its maximum safe-capacities have been under review, and so, as a result, we were allowed to increase our capacity for this conference to 510 delegates. This means that, if registrations do indeed reach 510, then we will fit into the Cathedral with no room at all to spare; and we will in fact exceed the capacity of the largest lecture-theatre in the TLC – a problem which can be solved by running a video feed from that room (TLC042) into the building's other, smaller theatre (TLC033).
This perhaps makes it clear why we need to emphasise that only paid-up delegates (i.e. delegates paying either the full registration or for the concessionary package) can be allowed into the academic sessions (including the plenaries, the two receptions, the concert in the Cathedral and/or any of the sessions at the Teaching and Learning Centre).