Wrexham suffered their heaviest defeat under the ownership of Ryan Reynolds and Rob Mac as West Ham ran rampant in a 6-0 rout on Friday.
The Welsh club has enjoyed a meteoric rise under its celebrity owners, achieving a record three straight promotions to reach England's second tier for the first time last season.
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But Wrexham were no match for a West Ham team that was relegated from the Premier League last season.
The six-goal loss exceeds the previous biggest defeat since Reynolds and Mac's takeover was finalized at the start of 2021 -- a 5-0 loss to Stockport County in the fourth tier in September 2023.
"Very tough," Wrexham manager Phil Parkinson said. "A very tough night. I've got to analyze myself and have that accountability. I'll be looking at what I should have done better."
The defeat came in front of the largest crowd ever for a match involving Wrexham, with 59,712 in attendance at London Stadium, which was built to host the London 2012 Olympics.
The previous record attendance was the 54,096 who watched Wrexham face Liverpool at Anfield in the FA Cup in January 1970.
Parkinson had said ahead of Friday's match that the whole club had been looking forward to the occasion in the capital.
But that enthusiasm will soon have faded as West Ham took charge. England international Jarrod Bowen and forward Joël Piroe put West Ham 2-0 up by halftime before the hosts inflicted further damage after the restart.
Konstantinos Mavropanos, Valentín Castellanos, Mohamadou Kanté and Manor Solomon all found the net to make it a night to forget for Wrexham.
The visitors were limited to a single chance throughout, though it could have had a significant impact, Mavropanos producing an excellent goal-line clearance from George Dobson at 1-0 before West Ham cut loose.
"For 25 minutes we were in it, then two moments where our defending wasn't good enough," Parkinson added. "The third goal really killed us.
"Part of me is being reasonable and saying these are a very good side, a multimillion-pound attacking force that should be in the Premier League."
The result continues a tough start to the season for Wrexham after narrowly missing out on a place in the promotion playoffs last season. Parkinson's team have just one win from their first seven Championship games and are closer to the relegation zone than to making a push for promotion to the Premier League.
West Ham, meanwhile, are on course for an immediate return to the top flight, with Friday's win -- their largest since September 2018 -- taking them top of the table ahead of the rest of the weekend's fixtures.
PA contributed to this report.