I had to dig-up our front garden path over the weekend (leaking water supply pipe - local water company not interested until the lockdown is over) and in the process found this 10mm clear plastic SWA cable buried in the ground. It looks way too small to be the mains supply (and I think that would black bitumen cable in anycase) but it does seem to run from the roadway to the house, although I can't see it in the utilities cupboard by either the gas meter or electrical service-head. Our BT phone line does come in underground but it looks overkill for a 2 wire phone line but you never know.
Anyone shed any light?