Why was that so important? Was that difficult to work out?

It ties back to the kind of foundational purpose of the Royal Observatory, so navigation at sea, and it's all about being able to find the positions of places on land, but also whilst on a voyage at sea.

And so essentially to know your exact location anywhere on Earth, you need to know both your latitude, which is your position north or south of the equator, and your longitude, which is your position east or west of a fixed location and lines of latitude and longitude are often you know seen on maps and globes as if they're real but they are just they're imaginary lines and so sailors could find their latitude Not easily, because you still needed particular instruments and you needed to be able to do a certain amount of maths, but they could find their latitude at sea by measuring the height of a bright star above the horizon, and by the 17th century they had a number of tools that helped them to do this, some of which were actually developed from earlier sophisticated instruments that were developed in the medieval Arab world, so representing that flow of knowledge exchange between cultures.

But finding longitude was much more complicated.

I mentioned that your latitude is your position north or south of the equator, so you have this kind of natural reference point to work with, but there isn't an equivalent for longitude.

Obviously, today, and well, from 1884, we start kind of officially measuring longitude through the prime meridian at Greenwich, but that was, you know... a decision that was made rather than kind of a natural reference point.

Instead, longitude is all about knowing the difference in time, local time, between two locations.

Are they just for decoration?