While I can understand the comments from those who've worked throughout, it's important to note that most of the infections arose within that group of people. i.e. If NOBODY had needed to leave their home to work, the epidemic would have been over a long time ago.
The trouble is some jobs you can't do without -hence "key workers".
From a "fairness" principle, yes, key-workers have carried a higher risk than those able to work from home, and maybe that's unfair... but leaving that aside, if EVERYONE returned to the office next week, then R would definitely shift upwards, infections would rapidly rise again and before you know it we're in the middle of a 3rd wave.
There's a separate argument that a 3rd wave doesn't matter (it does), but it's not really relevant here anyway as the government are determined to ensure a 3rd wave doesn't happen. Therefore if R rises, they will delay the further relaxation of restrictions and we all lose.
So in summary employers who have needlessly required staff back at the office, are as guilty, if not more, of prolonging the epidemic, as those who hold illegal raves etc.