I have been using this system for the last 3 weeks and The strike rate for this system is 100%.
The rules to this system are very easy.

1. Using the daily mail racing statistics.
2. There must be at least 7 years worth of statistics for the race to make this work.
3. Any race that has a strike rate for winning favourites of less than 20% is the lay.
4. Using betfair lay the horse who is favourite just before the off, if there are joint favourites? lay them both.
5. Don't just lay the paper favourite for the race, as this can change before the off. Please stick to rule 4 for this to work.

The price of the fav to lay can be quite large, in this case i would say only lay the races that have a favourite of no bigger than 3/1.