Without the aid of a time machine we can never be certain, but putting the various references together, in Domesday we have great areas of forest and fen, with settlements in a line at Low Hill, at Esmedum ( logic would dictate if it was a fort it would have been at the high point around Lodge Lane, and two more somewhere around Princes Park ( south of the fens) and Otterspool. The site of Liverpool north of the ‘pool’ inlet itself was a part of West Derby, the lands south of ‘the pool’, while of little use for farming, belonged to Smithdown up to the approximate area of Parliament Street.
By the time King John planned his new town, Liverpool was a separate entity, and all lands South of ‘the pool’ counted as ‘Toxteth’ manor ( incorporating Smithdown). These lands, swapped by the King with Lord Molyneux, were split the area into the Royal Park itself ( Toxteth Park), and the 'great heath' and Mosslake.
If this alleged swapping of lands with the King is actually true, it might explain the dispute between Edward Moore and Lord Molyneux listed in the Rental of 1667. When he owned the whole area, Edmund Crouchback gave the Mosslake fields to the Liverpool Corporation, who then sublet to Moore. Molyneux meanwhile, ‘Lord’ of Toxteth since the twelfth century, claimed ancestral ownership of the whole heath and Mosslake, arguing it hadn't been Crouchback's to give.
I'll give you a little breather from the hardcore before I go onto the next part and the meat of the story. I hope you'll excuse me but I'll skip the whole creation of Liverpool town itself bit, as its very well documented elsewhere, and after a few posts on other things jump to around 1600, which is when the story of the Moss Lake and what was to be Abercromby square really picks up again, and also links into the reasons for the creation of the first dock and Liverpool's explosion as a port.