Air Raid Precaution RG ARP unidentified company badge possibly related to Petroleum

A rare original Second World War period 'Air Raid Precaution RG ARP home front warden badge'; large pattern chromium plated circular example inlaid with blue enamel bearing cream diamond inscribed 'RG' with A.R.P below; the reverse impressed with maker's details 'Thomas Fattorini Ltd Regent St Birmingham'. Good condition, complete with original pin fittings, no enamel loss, minor stress marks.Diameter approx 32mm.Examining illustration in DOING THEIR BIT by JON MILLS there is a very similiar badge (C15) in every aspect except for the initials 'BP' described as 'BRITISH PETROLEUM'.