I have been able to create the same effect by installing a HTML Nugget in the sidebar then simply putting a small table in that nugget containg the photographs and links to the gallery.

Please consider this as resolved and once again, many thanks

The Plug ins are all standard using the install a new sidebar plug in button in the ACP.
THe plug ins installed are:
Quicksearch
Coppermine Thumbnails
Archives
Link List
Categories
Links in this article
Syndication

Following your suggestion I moved them all to "Hidden"
I then individually moved ...

Thanks for the suggestions yellowled. Never thought of trying that but gave it a go inside a Virtual Box machine. I used the Web Platform Installer and installed PHP 7.0.2. Serendipity version is 2.1.1 .
I also tried the suggested 2k11 theme.
Unfortunately still no sidebar. I think I will have to ...

If I use PHP 5.4 my sidebar displays correctly
Using PHP 7.1 I have No Sidebar.
Any Ideas? Thank you.