Frozen Eth

G'day. Many years ago, I bought some eth. The company went belly up/disappeared. Recently a bloke purporting to be from UK government agency contacted me in relation to this, stating that they had recovered my eth, and asked for cold wallet address, which I provided, and have now received frozen eth into of a substantial amount. He also stated that I need to buy 10% of the value of the deposited eth, and add to the wallet. Then I need to transfer both lots to another wallet in my name, which will thaw/unfreeze the eth in the process.

I am concerned that when I do the transfer after the purchase of the eth, that it will be stolen by a third party.

I suspect this is a scam, but I can find no evidence either way. I await your guidance.