What would be a legitimate interest?
Credico argued that S5 Marketing had been in receipt of confidential information, proprietary business know-how and training about how to organise campaigns effectively. This could have amounted to a legitimate interest, as is often the case in relation to franchise agreements (where the franchisee benefits from the franchisor's expertise in how to run the business). However, in this case, the judge at first instance was not persuaded that Credico had imparted any meaningful knowledge that S5 Marketing could take advantage of when organising future campaigns for competitors of Credico.
The Court of Appeal also noted that in previous cases where similar restrictions had been upheld, a legitimate interest had been found to exist where customers would have loyalty to the business which was the subject of the restriction. For example, it noted that this was a factor in One Money Mail v Ria Financial Services and Wasilewski (2015), which concerned money transfer services. One Money Mail had provided its agents with considerable support including training. However, customers' loyalty was generally to the agent as an individual rather than to the money transfer system's brand. In that case, the Court of Appeal accepted that the only way that One Money Mail could protect the investment it had made in supporting its agents was to impose a post-termination non-compete (also of 6 months' duration). The Credico case was different because it involved, for example, door-to-door sales or setting up "pop up" booths in locations such as shopping centres; this activity was unlikely to generate any customer loyalty from members of the public.
It's also worth noting that the Court of Appeal did not take issue with the High Court's finding that a non-compete obligation during the term of S5 Marketing's contract with Credico was justifiable; this was on the basis that Credico was entitled to expect S5 Marketing to devote itself to servicing Credico's clients during that period. However, for reasons explained above, the attempt to impose a post-termination non-compete was not justified.