Back a horse with bookie then lay on exchange

[Mark gray]

Hi guys. 

I follow a tipster and have noticed that every time a large price horse is tipped, its price plummeted on both the exchange and with bookmakers. Example is today a  horse was tipped at 16-1 and now it’s 5-1 with the bookies and the lay price is 7-1 on the exchanges. 

Now to me there seems a huge opportunity to lay the horse for profit. 

I’m looking for some advice on how to calculate how much to place on the lay bet to lock in a profit. Or if there is a better way to benefit this situation as it arises very often. 

Thanks 

[Sir Puntalot]

 to Punters Lounge @Mark gray   

It's all about timing and you can rest assured, the tipster will be backing the exchange price himself so it might not be easy as you think.  

I'm sure others will have their own point of view.