I'd be interested to read J Alfred Prufrock's views on the issue here.
Somewhere deep in the recesses of the BHA's Rule Book is the following:
92. Restrictions on laying to lose
92.1 In Paragraph 92.2, Listed Person
92.1.1 means any owner of a horse (see Rule 96), and
92.1.2 additionally, includes
92.1.2.1 where the owner is a Recognised Company, any director or Registered Agent
of the company,
92.1.2.2 where the owner is a Recognised Stud Company, any director of the
company,
92.1.2.3 where the owner is a Racing Partnership, the partners of the racing
partnership who are notified to the Authority under Rule 65.1.2 and who are not
Nominated Partners,
92.1.2.4 where the horse is subject to a lease, the lessor of the horse, and
92.1.2.5 where the horse is jointly-owned, is leased for one race only or is subject to
any other lease or arrangement registered under Rule 75, any Person who, at or
around the material time, played an active part in managing the horse.
92.2 A Listed Person must not
92.2.1 lay any horse he owns with a betting organisation to lose a race,
92.2.2 instruct another Person to do so on his behalf, or
92.2.3 receive the whole or any part of any proceeds of such a lay.
92.3 Any reference to laying a horse to lose includes any single instance of doing so, whether or not the single
instance was, or was intended to be, one of a series of betting arrangements.
92.4 Nothing in this Rule prevents the laying of any horse owned by a betting organisation in the ordinary course
of that betting organisation's business.
92.5 Betting organisation means
92.5.1 any bookmaker,
92.5.2 the Tote,
92.5.3 any company offering spread betting on horseracing or person-to-person betting exchanges
on horseracing, and
92.5.4 the employees of any such organisations.
I am still trying to ascertain whether there is another section, elsewhere in the BHA's Rule Book, covering: backing another horse in a race in which you own a horse; laying a horse which you do not own in a stable in which you own a horse; laying a horse registered as owned by a close family relative, such as your Mum, rather than by you; laying a horse when you pay some of the bills but are not among the named owners of the horse; backing a horse against a horse that someone you know owns; and much more besides.
As I would hate to fall foul of the rules through ignorance, I am going through them - the hundreds of pages of them - with a fine-toothed comb.
Will get back to you asap, though not necessarily this year.