The Skeleton in Grid Square C4: A Greyfriars Coordinate Challenge

There is a car park in Leicester city centre that has done more for maths lessons than most textbooks. Under its tarmac, in 2012, archaeologists found the grave of Richard III — the last Plantagenet king, killed at Bosworth in 1485 and buried at Greyfriars. The story is famous. Less famous is the fact that the whole discovery is a coordinate-geometry puzzle waiting to be solved.

So let’s treat it like one. Forget the trowels for a moment. Imagine you are the site supervisor with a clipboard, a scale rule and a grid. Your job is not to dig. Your job is to say, precisely, where to dig next.

A car park with a secret

Greyfriars was a friary, dissolved in the sixteenth century. Over the centuries its buildings vanished, its graveyard was built over, and by the twentieth century the area was a car park behind council offices. Historians knew Richard III had been buried at Greyfriars. They did not know exactly where. The 2012 excavation, led by the University of Leicester in partnership with Leicester City Council, began with a trench in the car park and ended with a skeleton under a reserved parking bay.

That is the headline. The maths is in the “exactly where”.

Set up your dig grid

Take a sheet of squared paper. Mark the axes from A to J across the top and 1 to 10 down the side. Each square represents one metre. This is your trench. It is not the real Greyfriars trench — it is a simplified training ground — but the skills are the same ones archaeologists use on site.

Now add some finds. A fragment of medieval tile at C4. A piece of window lead at F7. A copper-alloy pin at H3. A stone foundation running from B2 to B8. Plot them. Label them. Then answer these:

• Which find is closest to the south-west corner of the grid?
• What is the straight-line distance between the tile and the pin, to the nearest metre?
• A second trench begins two metres east of the pin. Give the coordinates of its north-west corner.
• The foundation is drawn as a line segment. What is its midpoint?

These are small questions. They are also the sort of small questions that decide where a real trench goes.

From grid to ground: scale and ratio

A grid on paper is useless unless it matches the ground. Archaeologists work with scale drawings, and so can you. Suppose your plan is drawn at 1:50. A line of 4 cm on the drawing represents 200 cm — two metres — on site. A trench 3 m by 2 m becomes 6 cm by 4 cm on paper. If a skeleton is 1.7 m long, how long is it on the drawing? If the drawing is enlarged to 1:25, what happens to those lengths?

Ratio is not an add-on here. It is the bridge between the clipboard and the clay. Get it wrong and your trench misses the grave by half a metre. Ask anyone who has dug a hole in the wrong place: half a metre is a lot.

Triangulate like an archaeologist

Here is where coordinates become detective work. Imagine two fixed reference points on site: a survey peg at A1 and a corner of the standing friary wall at J1. You have a bearing from each point to an unknown find. From A1 the bearing is 045°. From J1 the bearing is 315°. Draw both bearings. Where they cross is your find spot.

Now try a harder version. From A1 the bearing to the grave is 060°. From J1 the bearing is 330°. Plot the intersection. Measure its distance from A1. Convert that distance using your scale. Then check it against a third bearing from a point halfway along the south edge. If all three lines meet at one point, your coordinates are consistent. If they form a small triangle, you have a margin of error — and a decision to make about where to put the trench.

This is triangulation, and it is exactly the kind of reasoning that turns a scatter of clues into a location. It is also a lovely way to spend a maths lesson.

The forensic reconstruction

The skeleton itself adds another layer. Osteologists estimate stature from long bones using ratios. A simplified classroom version: if a femur is about one quarter of a person’s height, and a femur measures 43 cm, what is the estimated height? Give your answer in metres and centimetres. Then compare it with the known historical descriptions of Richard III. Does your estimate fit? What are the sources of error?

You can extend this into coordinates too. Suppose the skeleton is plotted on your grid with the skull at C4 and the pelvis at C5. What is the bearing from skull to pelvis? If the feet are at C6, is the body aligned north-south, or has it been disturbed? A single coordinate tells you a position. A set of coordinates tells you a story.

Why this belongs in a Leicester classroom

The Richard III discovery is local history with a global audience, but it is also a masterclass in problem solving. It asks pupils to plot, scale, measure, estimate and justify. It rewards precision and punishes guesswork. And it has a genuinely gripping payoff: the moment when the coordinates on a clipboard match the bones in the ground.

You do not need a real excavation to teach this. You need squared paper, a ruler, a protractor and a willingness to ask “where exactly?”. The car park has gone back to being a car park. The coordinates remain.

Try it this week

1. Plot the training grid and label the finds.
2. Draw the trench at 1:50 and 1:25.
3. Triangulate the grave from two bearings, then check with a third.
4. Estimate height from a femur and discuss the uncertainty.
5. Write a one-paragraph site report explaining where you would dig next — and why.

If your class produces a particularly neat solution, send it in. Leicester Maths is always happy to see a coordinate mystery solved with a sharp pencil and a clear head.