"I cringed when I saw those old salts wearing life jackets!!"
I agree - however, as was eloquently explained to me by Port of London, everyone, no matter how salty, was required to wear a life jacket. The reason is because they had real worries that had someone gone overboard without one during the pageant, then due to the sheer number of boats in the water, any rescue operation could have ended in tragedy.
Think putting well meaning man overboard recovery drills into place to get someone drowning in the river, and then causing a pile up, which in turn could easily have caused multiple collisions as people moved to avoid the accident. Lifejackets would have meant people stood a chance of floating, and giving RNLI vital seconds to get in and save them.
I saw multiple senior RN officers briefed on this, and go from 'what sort of nappy wetting loser wears a life jacket on the Thames' to 'very sensible measure, even if it looks gash' when they understood how much could have gone very badly wrong had someone fallen in without one.
As for the comments ref Belfasts size. Have you ever seen a T23 alongside Belfast? The two hulls are of near identical height and width, and Belfast is only about 30m longer than a 23. Its not the tonnage thats the issue, its the problem of dimensions.
T45s cant go through tower bridge without knocking the top off their radars, and that would definitely leave the UK at risk of golfball attack