Pure speculation then. Could equally be Russian agents seeking to further destabilise, or a local with a grudge, or commercial sabotage, or jihadists trying a new tactic, or kids thinking they are being clever.
The collective term you are looking for is bastards I believe, the rest is pure semantics dear boy
2009 4/4 Henrietta 1999 Indigo Blue +8 2009 4/4 Sport Green prev 1993 Connaught Green +8 prev