As the earth heats up Bill McGuire asks for information on the melting point of "everything from steel to my glass eye". Leo McKern did in fact have a glass eye.
Editor James Needs used stock footage from Hammer's The Quatermass Xperiment, also directed by Val Guest of a fire truck racing through the night past the patrol station in Bray.
In an early scene Jeannie is struggling with a Roneo stencil duplicator, saying it is "over-inking". The Roneo company threatened to sue the producers for the potential damage to the reputation of their products.
The realistic newspaper footage was shot in the Fleet Street offices of Express Newspapers and gives a vivid picture of the "old" London Fleet Street industry (most British newspapers have now moved out of this area, which was famous as a press centre). "Express" editor Arthur Christiansen plays himself in the film.
The scenes of the "Met Office" were filmed both outside and inside the Ministry of Defence Main Building in Whitehall. This access was remarkable. Those interiors were little changed until refurbishment of MOD after 2000.