The track from the coast path round the headland seems to work …
On the coast path at OS SS 745 935, at the fork just before the path goes downhill through the houses into Briton Ferry, take the track to the right (the only waymark at present is the one marking the coast path to the left, but the track to the right is very clear). This passes behind a kennels and contours up and down through the woods.
Ignore the turnings to right and left:
then at 747 946, where you join a wider track,
turn right and immediately left along a waymarked footpath downhill.
Follow this down to the corner of the Briton Ferry wood. Take the road ahead of you. At the T junction turn right, then when the road bends sharply to the right, take the track straight on.
Here there is a confusion of paths and we need some waymarking. The right of way (marked on the OS map as a byway for all traffic) is the one which bears to the right and becomes a hollow way along the edge of the woods
this looks like an old mining adit
When you reach the houses the track becomes a street called Gardners Lane. Follow the line of this street across Old Road
and down Herbert Road to the main road through Melincryddan. Cross the railway line by the footbridge ahead and to your right, then turn left over the canal bridge and left again to join the towpath towards Neath.
It’s only a little shorter than the route via Briton Ferry (just under 5 miles as opposed to just over – and both are about the same as the route via the dual carriageway bridge and the cycle path once that gets reinstated) but a more pleasant walk with less in the way of busy roads.
So – to sum up – Margam to Neath follows the coast path round the headlands via Brombil, Cwmafan and Baglan, turns right through the woods and down to Melincryddan, up the canal to Neath and down the Tennant Canal to the Abbey.
From Neath Abbey there’s a pleasant walk up the Clydach brook (industrial archaeology heaven – the Abbey iron works with its massive furnaces, plus dams and aqueduct) and a minor road takes you over the hill to Pontardawe. After that, the trouble would begin. (‘ “A long time before that, if I know anything about the roads” interrupted Gandalf’.) Still, we have Llantarnam-Margam sorted out, and Margam-Neath as a work of supererogation. Might be time to track back and tidy up Grace Dieu-Tintern-Llantarnam before we tangle with Carmarthenshire?