It's even less likely he jams signals where ever he goes and LSE just happened to notice it. His company would be very curious why he was disappearing. They can pull him on a screen and watch when he goes in and out of range. It would happen only to him, in whatever vehicle he happens to check out that day. A driver would have to be far more clever than that.

The article states "timestamps on trades made in financial institutions can be affected" There's your likely culprit; someone who for whatever reason needs to affect timestamps.