I retired a few years ago, but as I recall, the accounts would be drawn up as at the year end date and a Post Balance Sheet note would have been included which explained and showed the effect of the transaction.
I have never come across a transaction like this, despite being involved in some "interesting" accounting practices and quite a few normal property deals. I think you will need to see board minutes to get to the very bottom of this - assuming they are not too opaque. You could take profit on exchange, so again you need to see the documentation.
I will leave this one to more current accountants and enjoy my retirement!