In his line of work, Simon Thurley has seen his fair share of medieval cesspits.

But a cesspit that was recently discovered under a gallery in London, England, is unlike any the architectural historian has seen before.

The pit, found during a refurbishment project at the Courtauld Institute of Art, is nearly 4.6 metres deep and contains a wide array of artifacts dating back to the 14th and 15th centuries — including many items you might not expect to find in the sewer.

As It Happens host Carol Off spoke to Thurley, former chief executive of the charity English Heritage, about the history of the cesspit and what makes it so unusual. Here is part of their conversation.

I would think that once you've seen one cesspit, you've seen them all. So what makes this one special?

You would think that, wouldn't you? But I've seen a lot of cesspits in my life and this one is absolutely gargantuan.

The size of it was so big that when I was rung up and asked to go and look at it, the archeologists actually couldn't believe that it was a cesspit. But with a little bit more digging and a little closer look at it — it very, very obviously is.

It's sort of big enough almost to live in it. You know, it's that sort of size. It's house size.

You'd sit on your hole and do your stuff next door to the person who's sitting next door to you. You have a nice chat while you're doing it and then you go back to your work. - Simon Thurley, historian

What makes it a cesspit? What's the use of a pit? Especially this one that's this old.

Essentially, it's like a very large sewer that sits below the restrooms. It doesn't have a drain coming out of it and everything that goes into it sort of sits in there. It's very deep. It gradually rots away and seeps out through the bottom.

OK. So, it's not the waste that interests you — it's the things that have been found within it. What have the archaeologists actually found in there?

There's sort of two classes of things really. Things that accidentally got in there.

There was a very beautiful finger ring that obviously had really annoyingly slipped off someone's finger as they were, I don't know, wiping their bottom or something, and it plopped down into the cesspit.

Of course, there's no way you can get it out. So someone was pretty unhappy about that, and the archeologists were pretty happy.

A 14th-century gold-plated ring was found in the cesspit. (Museum of London Archaeology)

But that wasn't the only piece of jewlery they found down there, is it?

There were other bits of jewelry. There was a bit of a spur, which probably dropped off someone's foot. And a bit of a belt buckle. A little pendant.

There's also stuff that people threw in there. So there were things that people didn't want anymore, presumably because they were chipped, or damaged, or, you know, they fell out of use in some way.

So there's a lot of drinking vessels, lots of tableware, plates, jugs — all sorts of things. And they were all in pretty good nick because they'd just been lying there in this sort of pool of cess for the best part of 500 years.

Some of the dishes and cutlery — I mean, who tosses those in the pit?

Things get out of fashion. They get out of date. I really think they're deliberately thrown away because I think when you go to the restroom you don't tend to take a large pottery jug with you and accidentally drop it down.

This sounds like a pretty posh place with posh people who had been using it. So whose royal poop are you digging around in, do you think?

Actually, I don't think it was posh people who used this one and I don't think it was royal poop.

I think it was the servants who were using it because it was so big it couldn't have been designed for just one seat. There probably were maybe as many as 20 seats that emptied into it.

You have to imagine a superstructure on the top that had probably two sides to it — a man's side and a woman's side —and on each side there was a great, big, long board with a series of holes drilled into it.

You'd sit on your hole and do your stuff next door to the person who's sitting next door to you. You have a nice chat while you're doing it and then you go back to your work.

So, I think this was what is essentially a sort of communal restroom for the household servants of the Bishop of Chester, who's the senior bishop in England.

Thurley thinks everyday items like this post-medieval fork were probably thrown away deliberately. (Museum of London Archaeology)

Whose house was it that this was in?

It was the bishop. There were lots of bishops in that part of London.

This bishop in particular, the Bishop of Chester, had a large house with an outer courtyard and in his outer courtyard was this big communal restroom. At the time, it would have been called the "Great House of Easement" and all the big houses had one. This is just very, very unusual to find one.

And so a Great House of Easement is not the same as a public restroom.

It's only really for use by the bishop's household. But it was designed for a large number of people and actually mainly men because these households were mainly staffed by men. There were women too, but it was mainly men.

OK. Would they hang out in there? Would they become kind of a social thing?

It's very difficult because, of course, we don't really have any evidence to that. But what we do know is that they were a little bit less fussy about being private than we are today. They were happy to sit next door to each other.

And who knows? You may have said, "Oh well, you know, I'll see you in the Great House of Easement in 10 minutes."

I'm not sure.

Written by Katie Geleff and John McGill. Interview produced by Katie Geleff. Q&A has been edited for length and clarity.