I'm back at work after mat leave and I'm still pumping at the office. Currently I'm pumping in our "wellness room" (which was a supply closest when I started) which doesn't have a lock. Someone walked in on me last week.
I read up a bit and thought that it needed to be a lockable door but can't find the article. Does anybody know?
Have a look at the ACAS guidance here. You have a right to ask for a secure room but your employer isn't legally required to provide a locked room.
Can you buy a door wedge to put under the door on your side, or a door jammer if you think you'll be expressing for long enough to make it a worthwhile investment? Just something you put under the door from your side to stop the door being opened.