[cowholio4]

Whenever I see these big construction projects I see a bunch of big tools and people moving lots of dirt fast. So I'm always surprised when discoveries like this happen. Is it by accident? Or do the excavators have a team on hand looking for "treasure"?

[goatforce5]

This site is within the bounds of the old Roman city of Londinium and is well known to be loaded with archeologically interesting stuff (2000 years of continual habitation will do that). This exact plot of land contained the Temple of Mithras which was already considered very important:

https://en.wikipedia.org/wiki/London_Mithraeum

I'm told that lots of the office buildings in the area have Roman ruins just kinda bricked in and sealed in the basements. i.e., they get discovered during excavation, measurements are taken and whatnot, and while it's worth saving them it's not worth putting them on display and making a big deal out of it.

[jsizz]

The planning authorities have an obligation to consider the potential historical and archaeological impact of a proposed development, and can impose an obligation on the developer for a professional archaeological investigation (funded by the developer) prior to construction, as a condition of approving the development.

Or in other words: "We know this site is teeming with archaeology. You don't get to trash it unless you pay for a proper dig before you start"

[tragomaskhalos]

This particular site had already been uncovered before (I believe in the 60s); then, as now, a building was going up and the archaeologists had a limited time window to get in there and see what they could find. So in this case it was already known there was a Roman site there.

[RossM]

In the City at least, I think there are a number of procedures in place for this.

In order to get planning permission, developers need to do a historical/archaeological evaluation [0]. Occasionally I've seen notices to contractors at sites that warn work is to be halted if bones/pottery are found. I'm sure the nearby universities get involved with this as well.

[0]: https://www.cityoflondon.gov.uk/services/environment-and-pla...

[petewailes]

It's partly because they're so big. The actual surface area separating what will be in the bucket from what won't be is fairly small, and the bucket itself doesn't agitate what's in it as much as you'd think.

Also, at dig sites where there's likely to be historic remains in the UK, there's work done to ensure the conservation of the archeology likely to be uncovered.

It's called archeological excavation, if you want to do some Googling. Also, have a look at the Museum of London Archaeology. They do a lot of stuff with this.

Source: I work just down the road from three current construction projects going on at major archeological sites and asked them the same question.

[afarrell]

There is now some controversy[1] over how much work should be done in the name of archeological conservation. This work and the project delays it introduces comes at the expense of construction. There is therefore some amount of tradeoff with affordable housing.

[1] http://new.archaeologyuk.org/news/cba-response-to-new-neighb...

[13of40]

My dad was an archaeologist for the US government, and the bulk of his job came down to surveying potential construction sites to make sure they didn't destroy any anything historic. (Graves, stone tool manufacturing sites, etc.) This was in the more remote places of the Pacific Northwest, where most of what you'd find is hard for a lay-person to identify, much less assign historical significance to. I assume that in a place like London you can't dig a hole in your back yard without a team of archaeologists sifting through the dirt you take out.

[dghughes]

Or this multi-level basement craze by the super-rich in London. There must been artifacts found in at least one of these digs.

[Brakenshire]

It depends what you mean by historic, most of the basements will be areas first developed during the Georgian or Victorian periods. In the City of London and Westminster, which were the major historic centres, you aren't going to find many houses. Roman London was basically within the bounds of The City, and that is now almost entirely office buildings and some apartment blocks. This discovery is from about 1km² in The City, where Bloomberg Europe are building their new headquarters.