Thank you for comments above.
I have decided that I will definitely send an email to Dreweatts and Bloomsbury with a summary of my findings.
But in the meantime, as I said above, I thought it would be interesting to know what became of the sword from which the diamond was lost. And as is usually the case with me this bit of research has taken on a life of its own.

My first port of call was the catalogue of the 1891 Royal Naval Exhibition and yes indeed it was loaned for display there, but my heart sank slightly when I saw that it had been loaned by Viscount Bridport. Bridport was of course a descendant of William Nelson and had inherited many of the most precious Nelson artefacts - and then proceeded to sell them at an auction sale in 1895!
So jump forward to the results of the 1895 auction as reported in the Times. (Extract below). As you will see the sword was by then described simply as a "hilt" which suggests that the blade had been removed??!! But not only that. In addition the diamonds had been removed from the hilt and replaced with paste copies and the original diamonds had been made into a necklace!!
But something that really intrigues me is that the Times shows the purchaser of the sword hilt as Hood. And Hood of course is the family name of the Bridports. So it as if Viscount Bridport put all these items up for auction but another family member bought the sword hilt back.
I suppose Christies (the Bridport auctioneers) might know exactly who bought it or there might be some other way to track down where it is today, but I have pretty much run out of time for anything I am going to send to Dreweatts and Bloomsbury. I'll fire off an email to them this evening and watch any (if any!) developments with interest
ATB
Mark
PS There is of course a current Viscount Bridport. If all else fails he might know what became of the sword hilt!
Attachment:
Diamc.jpg [ 63.88 KiB | Viewed 12790 times ]