"complete a training flight of at least 1 hours duration"
Literally, I understand that to mean the flight (singular) must last 1 hour.
However, personally I would interperate that to mean at least 1 hour of training in flight and I would happily sign the log book if the flight(s) were satisfactory. Don't know what the CAA would do if they were recorded seperately in the log book and each flight was less than 1 hr.
I think the dual flight requirment makes good common sense and I would apply common sense by recording the seperate flights as just one.
The dual flight requirements are here:
http://www.ais.org.uk/aes/pubs/aip/pdf/aic/4W378.PDF
FIS.