Allen is still seen as a cult hero by Bees fans after leading them to two League One play-offs and two FA Cup fifth round appearances.
Since his exit the Bees have plummeted and their latest humiliation came with a dire display at Griffin Park against Luton.
It came hot on the heels of a joint record worst-ever defeat with a 7-0 thrashing at Peterborough on Saturday.
An angry mob of Brentford fans gathered in the forecourt after the game calling for the head of manager Terry Butcher and chairman Greg Dyke.
The Bees were no better than at Peterborough against a club embroiled in a crisis of their own.
Chris Coyne headed Luton in front from a tamely conceded corner on 36 minutes and Brentford had little in reply aside from a Lee Thorpe header saved by Dean Brill.
But in truth Luton could have already been running away with it after Clark Masters saved from Matthew Spring at point-blank range.
Sammy Moore almost equalised for Brentford just after half-time when his strike from distance was saved and Glenn Poole saw his free-kick tipped over by Brill soon after.
But Jaroslaw Fojut ended Brentford's hopes on the hour when he finished with a half-volley from a corner.
The performance of rookie left-back Darius Charles was one of the few bright spots for Brentford as he put some of the older players to shame with a composed performance.
A point of concern for Luton fans will have been the exit of Don Hutchison after just 27 minutes when he went off injured to be replaced by Darren Currie.
But in the end, the experienced Hatters back four had a quiet night and coped admirably with the aerial threat offered by Thorpe which Brentford were reliant on.