Okay, installed CRM 2013 and set up ADFS with IFD. Got it working.
The org was "crm" and the External URL was "crm.domain.com".
It was decided that the easiest way to migrate data from the old 2011 system was to import the organisation. It was called "org1".
Did that and then deleted the original org from deployment manager.
I expected that "crm.domain.com" would find "org1" as it is now the only org in deployment manager and therefor default.
However, when I access the url and enter my credentials, I get "There was a problem accessing the site...". I can access the internal url "internalcrm.domain.com" from the database server although the users get "There was a
problem accessing the site..." from other machnes.
In this scenario is there something I have forgotten to do at the DNS or ADFS level to get this working?
One strange thing that happened was the external URL actually worked for half an hour after the migration. This may have been some form of cache I suppose!!