So you work for Network Rail and need to dramatically increase capacity at Blackfriars station. Space around you is extremely limited. You can’t dig down because they’re busy building a new underground station for Crossrail. You can’t build up because, well, its a railway and trains don’t like inclines.
You are near the river though.
Answer: You build the station on the actual approach bridge itself. Ingenious.
It utilises previously ‘dead’ space for the platforms and thereby saves space on the ground for the ticketing concourse etc. It also allows for much longer trains.
Its an example of a bit of ‘thinking outside the box’ thats resulted in actually a far more elegant solution than could have been envisaged previously.