This is lifted from the BHA Rules of Racing:
53. Betting and betting contacts: professional riders
53.1 This Rule applies to Professional Riders only.
53.2 A Professional Rider must not
53.2.1 bet or lay a horse to lose any race with a Betting Organisation,
53.2.2 instruct another Person to do so, or
53.2.3 receive the whole or part of any proceeds of such a bet or lay.
53.3 A Professional Rider must not
53.3.1 associate on Racecourse Property with a Betting Organisation (or its representative), or
53.3.2 communicate directly or indirectly from such property with such an organisation (or its representative).
53.4 Paragraph 53.3 does not apply to any association or communication by the Professional Rider with the organisation (or representative) which
53.4.1 is part of the normal running of a race meeting (such as prize-giving and meeting sponsors),
53.4.2 is made with the owner of a horse for whom the Professional Rider is declared to ride, or
53.4.3 is expressly contemplated by Schedule (A)5 (information regarded as in the public domain).
53.5 A Professional Rider must not be present in the betting ring during a race meeting unless he can satisfy the Authority or the Stewards that he had good reason to be there.