The pre-trial is simply a formality hearing whereby a trial date is set. No evidence is seen or heard. Though the CPS do have an opportunity to ammend the original charge. In my experience the CPS are indeed very content on offering "no evidence", as seatrout suggested. Instead they will attempt to downgrade the charge to one that is less serious. What is the current charge against your partner at the moment??
Another point to note out is that if your husbands counsel can obtain the CCTV from pub accross the road (which should have been the police's duty in the first place), then defence counsel can put in an application for Abuse of Process, which is basiacally the failure of the Police to follow protocol in the investigation of a case. If the CCTV backs your partners story then this will help the strength of the abuse of process application because it shows prejudice from the outset of the investigation of this crime.
Be careful with character issues. Bare in mind that if your partners defence team assert his good character, then this will give the prosecution an opportunity to cross-examine him about any bad chracter issues and thus if he does have any previous for assault/robbery or other "relevant" offences, the court will indeed be made aware of this.
Hope this helps..