EGX 2020 is the latest in a long list (that also includes Comic-Con London as of yesterday) of major events to be cancelled in the face of the ongoing coronavirus health crisis. The show, arguably the biggest event on the gaming calendar here in the UK, was scheduled to take place September 17-20, with organisers no doubt hoping that the UK government would be able to put restrictions in place that would ensure events like this would take place.
Perhaps that was never feasible in the first place, but the UK's relaxed approach to Covid-19 restrictions has resulted in almost 70,000 confirmed deaths (so many of them avoidable) and, on a more superficial level, events such as EGX and Comic-Con simply aren't able to take place. At least not as planned.
With regards to EGX in particular, event organisers have confirmed a nine-day event in conjunction with PAX Online, taking place September 12-20. It's called EGX Digital, and it'll feature panels, demos, gameplay, competitive gaming, and more. It's also free, which is a nice touch.