Guernsey FC suffered the biggest home defeat in their history, losing 6-0 to Tooting & Mitcham.
The win saw the visitors go to the top of Isthmian League Division One South, while Guernsey drop to 20th place.
Chace O'Neill gave Tooting an early lead, before two Mike Dixon goals and one from Billy Dunn saw the visitors go in 4-0 up at half-time.
Dunn got a second seven minutes into the second half and Dixon completed his hat-trick in the last minute.
Guernsey's misery was compounded when striker Marc McGrath was sent off in the 88th minute for a second booking.