What is the official designation of the building visible from the Morpeth Arms in a manner enabling spying?
SIS Building The SIS Building or MI6 Building at Vauxhall Cross houses the headquarters of the Secret Intelligence Service (SIS, MI6), the United Kingdom's foreign intelligence agency. It is located at 85 Albert Embankment in Vauxhall, a south western part of central London, on the bank of the River Thames beside Vauxhall Bridge. The building has been the headquarters of the SIS since 1994.
Spy basket The Spy gondola, Spy basket, Observation car or sub-cloud car (German: "Spähgondel" or "Spähkorb" ) was a byproduct of "Peilgondel" development (a gondola to weight an airship's radio-locating antenna). They were used almost entirely by the Germans in the First World War on their military airships. The spy basket could be lowered from above through the cloud deck several hundred metres, in order to inconspicuously observe the ground and to help navigate the airship.