Version 9.1. Latest version at: http://wiki.ucl.ac.uk/display/AboutWiki/About+the+UCL+Wiki
Click the Insert/Edit Link icon (it looks like a chain) on the toolbar.
To link to a page in the UCL Wiki, search e.g. Global Spaces for the page. Put the name of the link in the Alias field. Click the link that appears after your search and click OK. (Attachments are included in the search.)
To link to a page on the Internet, click on the External Link tab and enter the address. (It may be safest to copy the address from your browser's Address field).