Robert Huth successfully completed a 45 minute comeback after injury but it was his fellow centre-back Steven Watt who made the main headline as West Ham were condemned to a late defeat.
Mick McGiven's men, looking to make it four wins in a row, found themselves trailing with only five minutes to go but in a display of defiance, Danny Woodards first and then Watt with a rare goal found the net to keep the Chelsea run going.
Huth by then had long been withdrawn, the first-half only his planned initial run-out since injuring an ankle for Germany against Nigeria in November. For a long while it looked set to be the most gentle of returns for our young international.
In the opening period the West Ham side offered next to nothing in the way of an attacking threat and keeper Lenny Pidgeley's main concern had been how to keep warm on a bitter night. Then on 35 minutes came the visitors' shock opener.
It arrived via a piece of pure opportunism from Moses Ashikodi. Latching onto a free-kick that had spun of Huth's head, the West Ham striker in a flash hooked the ball powerfully past Pidgeley.
Prior to that the game had been all Chelsea's although the scoring chances were limited. With five minutes gone, Woodards rose well but headed Sam Tillen's cross wide and ten minutes later it took a full-stretch dive by keeper Reed to keep out a Hollands' shot.
Then after Chelsea had gone behind, Huth drilled in a 25 yarder after the ball had been laid back into his path but it was struck straight at Reed.
Adrian Pettigrew was Huth's half-time replacement while the reserves' other German, Sebastian Kneissl, didn't even make kick-off. A late withdrawal through illness, his place in the starting line-up was taken by Joe Tillen, Chelsea switching formation to 4-3-3 instead of the intended midfield diamond in order accommodate the change.
Chelsea survived a scare just after the break when Pearson misdirected a good shooting chance but the fortune was with the visitors ten minutes into the half when Chelsea were denied an equaliser.
Woodards did well, acrobatically turning in a high ball at the far post after a free-kick had been headed on but his celebrations were cut short by the dreaded offside flag.
Time began to run out and West Ham looked on course to partly avenge their 5-1 drubbing at the hands of Chelsea in September. But then Pettigrew sent a good ball out wide to recent substitute James Younghusband on the right.
Waved on by the ref after doing well to bundle through Brevett's challenge, he laid the ball back to Woodards whose shot deflected up off defender Blewitt and looped into the net.
The celebrations were boisterous enough for that strike but nothing compared with five minutes later, the final minute of normal time. Chelsea won a corner on the right, Sam Tillen drove an excellent kick deep into the area and Watt, rising like a first-team centre-back should, powered a superb header into the top far corner. Every team-mate, Pidgeley included, joined him in the victory huddle.
In dramatic style, the Scottish youth international's first goal in four seasons of reserve team football had completed his side's first ‘double' of an increasingly profitable campaign.
Chelsea Reserves:
Lenny Pidgeley; Nuno Morais, Robert Huth (Adrian Pettigrew), Steven Watt, Sam Tillen; Craig Rocastle (James Younghusband), Anthony Grant, Danny Hollands (Capt); Filipe Oliveira, Danny Woodards, Joe Tillen (Jimmy Smith).
West Ham Reserves:
Matthew Reed, Tommy Laws, Rufus Brevett, Andy Melville, Darren Blewitt, Chris Cohen, Youssef Sofiane (Anthony Stokes), Sam Wright, Moses Ashikodi, Greg Pearson (Oliver Allen), Kyel Reid.
By Paul Mason