Ann: Removal from Official List, page-53

As it is illegal for a company to own shares in itself the purpose of a share buyback is to cancel them, thereby reducing the number on offer. The impact of the buyback is related to the principle of supply and demand - if there is a broad supply the price can be driven down. You will find that the company will buy its own shares at opportune times (perhaps if the price is at a perceived low) within the appointed timeframe in small quantities and at random times before cancelling them.

Purely speculatively, I think that the insiders who hold 64% will ultimately want to divest somewhat and if the SP stays up and the business is a successful they may do a 1 for 10 for instance, with a view to broadening the base. There is little benefit and a lot of risk to them in the longer term of having such a large position in a very tight register.