TfL - "Victoria Tube station escalator work completed three months early"
http://www.tfl.gov.uk/corporate/media/newscentre/21319.aspx

The overall works are far from finished though - the redevelopment of the
Tube station is due for completion in 2018.

The above press release includes this tidbit:
"The three escalators which run down to the Victoria line platforms and
which include the second most-used escalator in the world with 21 million
customers hopping on each year, were out of service one at a time, in
sequence, while they were being worked on."

Obvious question - what's the most used escalator in the world then?