dpc cream

Hi all, removing some skirtings we found injection holes, in a room which has damp problem. Was wondering if there is a known data when the (absurd) practice of injecting a DPC all started here in England, particularly South West?

I have a 1880 Terraced House and around the fireplace in the back room (it's closed off) I've noticed a very slight dark line appearing about 30-50cms above the floor. I think this could be the start of rising damp so I've removed the skirting board and the plaster is in good condition (i.e...