It was the first match for Brentford’s Development's squad in the inaugural U21 Professional Development League Two South competition .
Being deprived of several squad members, some of which on first team duty, it was a mixture of old and new in the named sixteen.
Goalkeeper Richard Lee - allowed to start as an over age player - was given a run out after shaking off a knee injury that flared up in pre-season.
In truth he had little to do except for the three goals that decided the game, all of which arrived in the first half.
Millwall - managed by former Bees boss Scott Fitzgerald - went ahead in the seventeenth minute in a game that necessitated several water breaks to cope with the hot weather.
A crowd of Brentford players failed to deal with a long throw, Lions striker Connor Wilkinson lashing the ball past Lee from twelve yards out.
The Bees hit back shortly afterwards, Antonio German heading narrowly wide from a Kamau corner.
The next two big chances fell the home side’s way before they increased their lead with seven minutes of the half left.
Brentford defence did not deal with a low left wing cross that Jason Twum simply tapped in from five yards out.
It was even worse in the 42nd minute – a clamitous attempt by Pierre, Onovwiun and Griffiths to all try for the same ball in the air ended in failure, the ball running kindly for Wilkinson who slotted home.
Trialist Ben Checklit, latterly of Kingstonian, replaced Clarke at the break but he only lasted for 30 minutes before being withdrawn himself due to injury.
Brentford: Richard Lee; Richard Bryan, Michael Kamau, Aaron Pierre; Sam Griffiths, Josh Clarke (sub Ben Checklit 46 (sub Max Herbert 75)), Michael Onovwigun, Lloyd Harris, Aaron Scott, Tyrell Miller-Rodney, Antonio German.
Sub (not used): Louis Bragg.
Millwall: Luke Bartlett, Danny Newman, Dylan Richards, Danni Shitia, Jake Goodman, Will De Havilland, Tobi Alabi(sub Joe Guinchard 90), Jack Sammoutis, Aiden O’Brien, Connor Wilkinson (sub Connor Callaghan 75), Jason Twum (sub Callum Webb 85).
Sub not used: Tom Bladle.