Unbeaten in their first two top-flight games and, with just one defeat in their last 15 matches stretching back to the spring, unchanged West Ham had kicked off looking to build on their bright start.
And within the opening quarter-hour Yossi Benayoun and Marlon Harewood went agonisingly close to putting Hammers ahead against a Wanderers side that had seen Bruno N'Gotty replace Radhi Jaidi following their midweek win over Newcastle United.
Midway through the half, however, the lively Stelios Giannakopoulos almost celebrated the signing of his new three-year contract with a goal, but with the whites of Roy Carroll's eyes in his sights he scuffed his volley straight to the Hammers goalkeeper from ten yards.
The Greek playmaker then suffered a total communication breakdown with Kevin Davies just three yards out, while, at the other end, Jussi Jaaskelainen performed wonders to deny Benayoun and then Danny Gabbidon.
But it was Harewood who came closest to breaking the first-half deadlock when Teddy Sheringham sublimely chipped him clear in stoppage-time, but again the powerful striker wastefully volleyed over the top to keep it goalless at the break.
Five minutes after the restart, El-Hadji Diouf was booked for kicking the ball away before being replaced by the subsequently influential Campo, who quickly clattered Harewood and then scorched the Hammers' crossbar from 30 yards.
If the Spaniard was busy then so too was referee Phil Dowd who also dished out yellow cards to the dissenting Tomas Repka and over-physical pair of Davies and Stelios.
As the hour mark approached, the Trotters finally got their noses in front when the hitherto subdued Jay-Jay Okocha unleashed a low 18-yarder which cannoned off the goal-guarding Benayoun to Davies, whose mis-directed shot was bundled home by Nolan from close range.
West Ham responded by introducing Jeremie Aliadiere and Bobby Zamora and when the galloping run of Arsenal's on-loan Frenchman was halted 20-yards out, Sheringham's curling free-kick crashed out from the underside of Jaaskelainen's crossbar.
The Finnish shot-stopper also palmed aside Nigel Reo-Coker's low 20-yarder, but by now West Ham were chasing the game against a Wanderers side giving little away in any area of the pitch.
And when Okocha's searching pass released Campo behind the pushed up home defence, the Spaniard kept his head and coolly threaded a low ten-yarder around the exposed Carroll.
Sheringham showed equal composure to drill his last-gasp penalty beyond Jaaskelainen after Hayden Mullins was upended by Nicky Hunt, but it was too late to prevent the Hammers from succumbing to that first Premiership defeat.
Man of the Match: Stelios Giannakopoulos
Following an energetic and enthusiastic display it wasn't all Greek to West Ham to see why Bolton are so happy that their influential midfielder has signed his new three-year contract.