How to tax mined coins in a prefarm

I mined a cryptocurrency during a prefarm meaning it was not listed on any exchanges and therefore had 0 value at the time of being mined. After a few months the prefarm ended and the coins suddenly had a value as exchanges listed it.

I’m from the U.K. and from what I’ve read mined crypto is taxed as income at the time of receiving it. Does this mean I pay no tax on the coins I mined in the prefarm? Or does it mean that I’m taxed at the initial price when the first exchange listed it? Thanks.

Is the coin now listed on CoinMarket Cap?
I believe it would be $0 if it was not tradable yet. Therefore you would be taxed at the time of received which would be $0.

Here is the breakdown of classifications: https://hub.accointing.com/our-crypto-platform/report-taxes/the-different-types-of-crypto-transaction-classifications
Here is how you are taxed per classification: https://hub.accointing.com/?s=Specific+tax+classifications&id=3300&post_type=post