It's a Faraday Shield he has done and just basic physics blocking the signals.
Only thing is it will also probably interfere with any headphones and WM08 so would need hard wired headphones to the...
Watch out for those salties :)
You should have got the guy with the lawnmower to cut the grass for you :)
Stay safe Gary and hopefully after this virus has gone you can get back up here for a dig...
Back on the Romans with Celtic for good measure.
Hunt dedicated "To The Fallen" as my tribute to those who have lost their lives over the years. Lockdown coming up so no more hunts for four weeks.
As John said also have you gauged the size of it with in pinpoint.
At that depth and if wide signal probably large iron, if a narrow signal I would still dig it.