Long before I was into aviation I was a qualified Town Planner (dreary jobs, glad to get away).
One of the things that comes out is the lack of joined-up thinking between different government departments. The CAA allocates helicopter route H4 along the Thames, tightly squashed in under the LCY (who were on easterlies that morning, thus making their turn onto finals overhead Vauxhall) 09 approach at under 2,000 feet. Meanwhile another government department, it seems to be the Deputy PM's office this week, happily gives planning permission (because although ostensibly done by local authorities, all the "biggies" come to government attention) for some of the highest structures in the country right on the same route. This one was right on the Battersea approach from H4 at 700 ft.
You also have to wonder what the developer was thinking in the first place, putting that up into a known and published helicopter route. But avoiding such issues is what Planning is about. Goodness, it nit-picks over the most trivial details. This was not trivial.
The one that has previously concerned me is The Shard at London Bridge. Over 1,000 ft high and again right on H4. Remember that one of the clearances given to this aircraft was to go east in the hold as far as London Bridge. Which is The Shard location. And where a holding aircraft would be doing a 180 degree turn over the river in tricky visibility.