One very ovaled hole.
I wasn't at all sure at first how I was going to get it at because access from below is severely restricted by the manifold down pipes and access from above is severely restricted by the starter motor. In the end it turned to out to straightforward. There was just enough room to slide a ring spanner between the manifold downpipes and the chassis rail to undo the nut from underneath. Getting the washer and nut back on the new mounting bracket was a bit of a fiddle but with the help of some lateral thinking and some sellotape even that got sorted quickly.
Should get the rest of the front suspension back together and road tested on Friday afternoon.
On another subject, I removed the O/S engine valance this afternoon when I was checking out access to the wishbone mounting bracket and was surprised to notice that there was quite a lot of liquid sloshing about in the catch tank, which is mounted on the front of the O/S engine valence.
It turned out to be about 300ml of water:
I suppose some condensation is inevitable but I wasn't expecting to find as much as this. I think I'll post a question in the Club Triumph forum.