I now have 2 users whose names are not correctly displayed in the 'welcome' menu at the top right of the page.
The first user married and her surname changed. The new name was entered in ActiveDirectory but her maiden name is still displayed.
In the second case, a LAN id was reallocated to a new department member. The name of the previous user is displayed in the portal.
The AD synchronising appears to be running every night and I can see no errors there. The AD entries for the 2 users appears correct and no hint of the previous data.
What else can I do to force an update of the user information?