The result - somewhat ironically clinched by a stoppage-time goal from Johnson's final signing, Jonathan Obika - lifts them back into the League One play-off places.
Youth-team boss Oldfield said: "The players had to re-focus after the surprise events of the past 24 hours and they did that by delivering an honest and hard-working performance.
"The game wasn't a classic by any means but we responded well after Brentford's equaliser and got our rewards in the end.
"Jonathan did well and effected the game in a good way after he came on. He has done well on loan at this level in the past and it will do him good to get his first goal here.
"I didn't learn I would be in charge until late in the day but you always have to be prepared in football and all the staff deserve credit for this result. It showed that everyone is together and it is obviously nice to be into the play-off places, although everyone knows how tight this division is this season."
Source: PA
Source: PA