Paul Burridge wrote:

This must be a major embarrassment for the security services in
Britain.

Did it have "if found please return to MI5" stamped on it? You don't know
who made or installed it.

The sheer size of this thing, I mean. And the fact that it
appears to have been designed about 60 years ago and runs off dozens
of penlight cells. Hardly state-of-the-art!

"Party chairman Mitchel McLaughlin said it was a highly sophisticated
device with a large battery pack and the party had no idea how long it had
been in place."

He and you apparently have no idea when it was installed so you have no
idea what the state of the art was when it was made.