Thanks @Jean_Pierre_Traets
A gif probably shows the issue better than an explanation.
Hope this explains what I mean.
The main table (detail view) is what the user interacts with.
They select from a bunch of lookups.
However, it is very easy to accidentally open a lookup option, and change it. And once its changed, it effects all the data in the doc. This particular one is really obvious, but not all are. One of our staff accidentally changing something a few weeks ago broke things for them and we only realised 3 weeks later causing significant probs.
The allow quick adding of new items is off 
My question is what can i do about it? Seems odd I can change something that is in a read-only table.