Employers should take care when asking a new recruit to attend meetings or events prior to the start date of employment specified in the contract. The date on which continuous employment began could be brought forward (so that unfair dismissal rights are accrued earlier).
It will be a question of fact and degree whether the activities can be seen as performed under the contract of employment. This will be much less likely if attendance is not compulsory and if the time is not paid for. It may also be relevant if the employer regularly sends non-employees to attend such meetings. (Koenig v Mind Gym, EAT)