Has this any failings do you think? The door can be replaced.

The house was built in the 1890’s on Cathedral Road and the power station was built 1894, at that time horse trams running past the house and were electrified in 1902.

So it is actually possible the house had an electric supply from when it was built and it could have had a D.C. supply.

In 1923 the electricity supplies to consumers were:

• 6,600 Volts, 3-phase, 50 Hz AC
• 400 & 200 Volts, single phase, 40 Hz AC
• 400 & 200 Volts DC
• 550 Volts DC Traction

https://en.m.wikipedia.org/wiki/Cardiff_power_stations

I did wonder if it’s possible for the pitch filling to have been attacked by woodworm.

No I think not. It is too sticky and chewy for wood boring insects.

Z.

No I think not. It is too sticky and chewy for wood boring insects.

Z.

The backboard would seem a preferable choice.

I think personally I'd pass on eating either. But there are quite possible bubbles or even quite long tunnels where either air or moisture was entrained when the tar was originally poured that leave it slightly porous or indeed some lighter hydrocarbons oils or paraffins  were in the mix that have evaporated. - cold applied roofing tar  - the stuff dissolved in naptha, often sets slightly bubbly for the same reason. Tar from the gas works did not always have a well defined make-up, it was just cheap waterproofing and long lasting. Before modern plastics there really were not so many choices

The mice ate the caps and nozzles on my cans of WD40 and are quite partial to PVC insulation, so I suppose it’s a matter of personal choice.

The CC on the head presumably is Cardiff Corporation so puts it pre-1948, so between 74 to 128 years old.

I would inclined to go towards 128 years old rather than later.