Looking at BRS in/out diversions details from another forum that is usually reliable with such information, it shows that BRS was open on the days earlier this week when lower-lying airports in the vicinity were fogbound, including CWL and Filton (FZO).
Several inbound CWL flights and one FZO inbound (bmiRegional) were diverted to BRS including Eastern from Newcastle on the morning of 1 March.
There is a note saying that passengers were bused from Cardiff to Bristol for the flight back to Newcastle. That might be the reason for any overall delay.