Looking at Musket post, fully agree with paras 1,2,4.
Don’t think using a second rwy at destination as an alternate stacks up. If 27L at LHR is out due weather then so will 27R and at the planning stage the weather requirements for alternate are more stringent than for destination.
That said we are allowed to do it but the weather has to be pretty good (2000’+, vis 5k+) but I can’t remember it in the last 20 years.
rgds
ps. Who doesn’t love Cat3 ops?!