No 6, also of London part of the current name, but good enough for goverment work! lol You're up Coenharbour !!!
well done, I was searching, an just found this link a hair too late. http://no4.homestead.com/Home.html
Haven't cracked the code! The only thing I have come up with is an Ocean Alexander. That can't be it.
Another clue: The designer has worked with Pieter Beeldsnijder (1983) and the recently disceased Willem de Vries Lentsch (1985).