I think David has won as Jason as left his wife and believing Sarah's evil brother, how come Gail, Aurday and Jason can't see what he has been up to, this is what David has done so far

1. Nearly killed Sarah's daughter & Jason

2. Faked his own death

3. Texting messages to Becky from Jason's phone

4. Playing mind games with Jason thinking Sarah's evil.

5. Playing mind games with Sarah making her think Jason is cheating on her.

6. Burning his exam papers.

7. Lying to the court about Tracy when she had murdered Charlie.

8. He has now spilt up Jason and Sarah.