To the glass itself,
Aviation glass (windshields in particular) are pretty thick and safety laminated so that the glass holds together even if there is a crack. Similar to the windshield on your car if you have ever seen the aftermath of debris striking it. And depending on where the crack was in the glass - imagine looking at the profile of a Big-Mac, many layers put together, same concept on this glass - it could "look" a lot worse than it actually is.
That said, descending to FL100 and a slow cruise on over to LHR eliminated most of the pressure differential between cabin and atmosphere, leaving just wind resistance as the main force on the comprised glass surface.