A simple system simply purchasing a small amount of shares whenever a director makes a large purchase. Results below.
There is no set criteria for buying aside from that a large purchase (£250,000 aggregate) must be made, and purchases can be avoided if I I already own the shares, director is making an initial purchase, or if they are simply buying back a previous sale.
Shares must also meet my own criteria of having a target price in advance of the current price. This is an optimistic estimate based on cashflows so most should qualify.
Staking strategy is to simply top-up account with £100 at each trigger, and to buy the maximum number of shares with the cash in the account. This will vary (and hopefully increase) over time as dividends accrue in the account.
These type of trades are only made possible via Trading212, who offer zero fee commission trading on certain equities. Visit them here.