The BBC is currently showing a dramatisation of Joseph Conrad’s novel The Secret Agent, written in 1907. Conrad was partly inspired by the bizarre story of the anarchist Martial Bourdin, who officially became Britain’s first suicide bomber in February 1894 when a bomb he was carrying exploded in the park near the Royal Greenwich Observatory.

In the drama, starring Toby Jones (Dr Zola in Captain America, and the voice of Dobby in Harry Potter!) plays Verloc, a shabby pornographer and informer secretly in the employ of the Russian embassy. Verloc’s new Russian handler, Vladimir, tells him to organise the detonation of a device at London’s Greenwich Observatory, in a scene that shows them walking past the famous Shepherd Gate clock:

Vladimir tells Verloc to forget about trying to assassinate public figures:

The sacrosanct fetish of the day is science, it’s become the new measure of progress; of how the world is ordered, civilisation moving forward. And here, we have the prime meridian, zero longitude, the centre point of the earth, that divides the world into two, that orders the world, Eastern and Western. One line, emanating from this building, in Greenwich.

To which Verloc replies, incredulously:

Blow up the observatory?

As with all BBC productions (the recent series Jonathan Strange and Mr Norrell was another example), the period details — the drama is set in 1886 — are beautifully rendered and convincing, although of course nothing is ever as real as it looks.

In typically ingenious fashion, most of the London scenes were shot in Glasgow, which has a more realistic Victorian London vibe. Fortunately, the Shepherd Gate Clock and the Greenwich Park surroundings look authentically Victorian. But in fact much of this is also a recreation, albeit a real and necessary one. Here’s what the Shepherd Gate looked like in the 1870s:

The more substantial differences between the two scenes can be attributed to another bomb, one dropped on Greenwich in 1940 by German bombers during World War II.

If you’re very observant, you’ll notice that the 1870s photograph shows the clock as reading 23:20, whereas the 1886-set 2016-filmed TV show has the clock showing just after 12, although both scenes look to be set during the daylight hours. If you want an explanation, have a look at this old post!