ESPN’s Don Van Natta Jr. and Seth Wickersham published a long investigative report on Tuesday, detailing the history of the Patriots’ run-ins with the NFL when it came to bending the rules.

Tracing from Spygate to Deflategate, the report looks to provide context as to why the NFL was so hell-bent on pursuing a harsh punishment for the seemingly innocuous act of playing with slightly under-inflated footballs.

One of the most damning parts of the report is when Van Natta and Wickersham get confirmation from anonymous former Patriots employees that the team used to send an employee to opponents’ locker rooms to steal their play sheets.

From the report:

In fact, many former New England coaches and employees insist that the taping of signals wasn’t even the most effective cheating method the Patriots deployed in that era. Several of them acknowledge that during pregame warm-ups, a low-level Patriots employee would sneak into the visiting locker room and steal the play sheet, listing the first 20 or so scripted calls for the opposing team’s offense. (The practice became so notorious that some coaches put out fake play sheets for the Patriots to swipe.) Numerous former employees say the Patriots would have someone rummage through the visiting team hotel for playbooks or scouting reports.

This seems considerably worse than footballs being deflated, and can perhaps explain why the NFL was so eager to punish the Patriots.

You can read the entire report over at ESPN.

UPDATE: The Patriots have issued a statement about the report.