One consequence of sharing some stations with other train operating companies is that we get the fallout when their standards slip even lower than ours.
So spare a thought for station staff at Moorgate, Old Street and Highbury & Islington. Great Northern have omitted to clean their tunnels properly for a couple of decades, and the dust has now become a positive nuisance. The good news is that it doesn't - as initially feared - contain asbestos. The less good news is that it contains mould and various other nasty substances.
It is just not acceptable for us (or our Great Northern workmates) to be subjected to working in these conditions.