Exposed External Metal Trunking. Easily Touchable.

Do you think that the trunking is earthed, or will it just contain S.W.A. cables and not be earthed, as likely the supply is P.M.E?

Could be either.

The regs. seem not to prefer large outdoor metal conducting masses connected to a P.M.E. supply, such as caravans and steel hulled boats etc.

Caravans/boats (and electric cars) are perhaps special-ish cases in that we'd expect people to regularly grab hold of them and perhaps in less than ideal conditions (wet or no footwear etc). There's little aversion to PME with other equally large or larger metallic structures - e.g. lamp posts or the outside of steel framed & clad buildings or even steel bridges.

  - Andy.

outside of steel framed & clad buildings or even steel bridges.

  - Andy.

Probably safer as they are naturally well planted in the ground and well earthed unlike the metal trunking run along the wall.

Z.

Being a supermarket plus car park of the dimensions you suggest it's probably got it's own HV supply with a dedicated transformer, so I would guess more likely TNS or PNB. It may also have a buried earth electrode around the perimeter for the LPS tying it down fairly well, albeit inadvertently.