Puddles on flat lead roof

[FB]

Hello

I have recently had my leaking flat roof above a bay window replaced. The builder has put down lead and sloped it so water collects at the back and should drain off to one side, but there is now a puddle at least 5mm deep on the roof, against the wall of the house. Should I be worried about this?

 

[Mw Roofline]

Well put it this way nothing is gonna get through the lead but can't see the job so difficult to comment further.