TOM CRUISE filed for divorce from NICOLE KIDMAN because he discovered she was having an affair.

Sources close to the actor are breaking their silence to reveal that once Tom believed Nicole was cheating, it was the final nail in the coffin to an already troubled marriage.

One pal says, "Tom feels he has proof that Nicole was having and affair. And once he came to the bitter realisation he cut her out of his life with the coldness of an executioner.

"Ever since the split, Tom has cryptically been quoted telling people Nicole knows why he dumped her - and left it at that. But the reason is he believes she cheated on him. "She keeps saying she has no idea why he is treating her so callously and divorcing her with such lightning speed. But she knows all too well." (SVD/NE/RP)

Source: WENN