Actually, that's not the case. Anything published before 1971 in the UK would have been priced in our old currency, which would have been "d" or "1 /-" prices.
We changed our currency to Pence "P" prices in 1971.
Just to confuse matters.
Thanks for undoing my misinformation. So, what did "D" stand for?
"Denarius".
First minted about 211 BC. Italian common noun for money: denaro. In France,the denier. Arabia & Serbia, the dinar. Macedonia, denar. Spanish dinero. Hence "d" as the abbreviation for the British penny prior to 1971.