Double-barrelled 'geofizz'

John Gater and his geophysics team have been trying out a new piece of equipment for this programme: two magnetometers, interlinked, and strapped to a special frame. So what's the deal with this serious-looking bit of hardware?

'This is a great new piece of kit,' says John. 'Essentially, it doesn't do anything new, but it does allow us to do a survey in half the time. A 20-metre square can be done in just three minutes – and that sort of saving really adds up by the end of the day.'

The team has also been using resistivity to determine features under the ground. 'We've had good results,' continues John. 'By changing the arrangement of probes, we can "see" deeper into the ground. We've managed to find the original plan of the church on the triangle, and then by looking deeper we've also plotted the deepest foundations – which could belong to an earlier-phase smaller building, before the tower was added.'

On top of these tools, the geophysics team has also been using ground-penetrating radar. 'The radar results have been excellent,' says John. 'By layering data sets as we go deeper (like a sponge cake), we can then peel them away on the computer back in the incident room. We can look at the ground and then lift off slices on the computer screen. You start off with a green splodge of topsoil and then go through the backfill to see the outline of wall foundations. Doing this, we've been able to see about 2.5 metres into the ground.'

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