Hi Martin,
Mon plaisir mon ami😉
"I am not sure quite how he managed to do this."
No rocket science Martin. As I understand the situation-
Posting videos via YouTube was introduced to avoid flooding the available server space with Mega / Giga bytes of files, especially now in the days of HD / UHD camcorders and Dumbphones which produce huge files.
I've long suspected that there is an Upload limit, just like with many email services, of about 15MB. Your video fell just under that at 14.7 MB so it worked😊
I simply used the normal "Select Files" procedure to suck and see!
I sucked - and we all saw😉 I did the same with Ron's "Fishtailing" videos.

I propose to conduct a few tests with other videos to prove the limit.
(Assuming that Stephen doesn't read this and just tell us!😉)
I'm hoping that the recent site upgrade also included a server upgrade to provide more archive space as the site grows and develops. The last part is our job fellow constructors and sailors👍

Re YouTube account: I only opened one last year so that I could post my Sea Scout sea trials vids which varied from 69MB to 252MB in 1080p HD format.
I'm not a regular UTuber by any means. Registering is free and simple.
Only difficult bit is remembering the damn password if you don't upload regularly🤔
Happy and successful building, sailing, uploading and viewing folks.
Cheers, Doug 😎