So I bought some new taps as the old tap corroded in the middle and snapped so it needed to go.
I took the old ones off which never leaked before and popped the new ones on.
Replacing the washers, but keeping the existing lock nut.
Now on the hot tap only, the nut as in the picture has started leaking. Using a basin wrench I have tightened it to it's absolute maximum and it hasn't made a different at all. What are the suggestions here? Do I need to get a new nut? If so how the hell do I get it off?