Has anyone come across a 2m or 2.5m SDS drill bit. Another option (depending which way I can drill the hole and what the bit finds itself going through) would be a drill bit of that length which can drill through soil (mosty soft clay, which I think would hold its shape for long enough to feed a lining pipe through afterwards, but does also include some stones and old smashed roof tiles).
Trying to think how I can drill a hole under a patio and through the wall into the subfloor space, for theading cables.