And what has happened since the Network Rail Assessment in 2017?

Their conclusion filed as evidence for the Brewery Inquiry was:

” even though Network Rail is currently managing the risk as far as is reasonably
practical at Mortlake it is the recommendation of this risk assessment for Network Rail to
engage with the local council/developers to not only establish possible user impact but to
broach mitigation options. At the time of writing a meeting with representatives of the
developer is planned for August 2017.”