Atlantic 21 and D Class maintenance manuals RNLI
Think the EA version of the D class had 2 anchor line lengths depending on local operating conditions ,
standard was something like 40 metres or a longer 50 metre could be ordered depending on local conditions ect .
As SAR said the end of the line was secured with a bronze eye bolted into the bottom of the Anchor box
then run through the carabiner on the front of the bow dodger ,
the line could then be adjusted & made fast using a grab handle or the more secure Figure of "8" ( mountaineers descender ) normally used when Veering that is secured with a very short strop to the starbd side lifting eye on the floorboard .