Simon Cowell's affair with Lauren Silverman, who's pregnant with his child, was reportedly going on since 2009, long before she separated from her husband.
When did Andrew Sullivan find about it?
Cowell's relationship with Lauren Silverman earned him a place as a co-respondent in Andrew's divorce filing, but what he knew and when is unclear.
Some sources say she would spend hours on the phone at her home talking to Simon, and Andrew - also his close friend - heard the whole thing.
According to certain friends, Andrew clearly knew that Simon was banging his wife, and they think the faux outrage he's expressing now is a crock.
Other sources close to Andrew paint a somewhat different picture.
Looking back on events, there may have been plenty of "warning signs" with the benefit of hindsight, but he just didn't pick up on them at the time.
They also say Andrew knew Simon and Lauren were "flirting," but didn't necessarily pick up on the fact or assume they might be sleeping together.
The couple's divorce, meanwhile, is at a standstill.
Cowell wants it to be settled ASAP, putting to rest the notion that Simon is a home-wrecker, but custody of their 7-year-old son is the big sticking point.