Thanks everyone.
It seems from your comments that when viewed on an 'optimally' set up computer a link to a final post on a page in the thread should still work. However in practice in the real world it can't be relied upon and some people are having problems. (I have tried clearing the cache and cookies on my mac and windows machines but still get a problem.)
There are three methods of linking from the index that I can think of:
a. Link to the external picture hosting account/location. (This was tried originally but resulted in problems when people wanted to remove their photos. Either myself or a moderator had to then edit the index in addition to the poster removing their original post, which with 30+ pages was no longer easy to find.)
b. Link to the post number in the thread. I understand from the comments above that theoretically this could have problems if an earlier post is removed as all subsequent posts will be renumbered.
c. Link to a post by its system number. ie. link to the 3,456,789th post ever to appear on PPRuNe. (This is the current way that the index is set up but it is much slower to display the correct post on screen than method b.)
If anyone can think of any other possibilities that I can try out I would be grateful.
One thought that I have had is this:
If I created a new thread, with the index at the front, might a subsequent merging of the two threads by a mod create a clean thread and get rid of the 'problem' that has now appeared in the original one or would the corruption be carried across? I suspect that there is only going to be one way to find out.
Thanks again for your help,
eticket
(I am sorry but I will now be without the Internet until Monday so I won't be able to reply until then.)