If it helps this is a tale from over 35 years ago (and God does that realisation suddenly make me feel very very old)...
Also, No idea if they made tea for anyone else at the time.
I can't quite remember the tea conveyor belt set up all that years later, but you'll get the gist.
So, right at the very top of the building there were some fixed windows and the glass panels were starting to come away from the frames. We were sent up with a ladder, a hand brush, and a large floor brush and dustpan (way too big, heavy and cumbersome to take up a ladder) and some tubes of mastic to fix the issue before the glass fell on someone's head.
So I go up the ladder, use the hand brush to brush off many years worth of accumulated dust, dirt and dead flies and spiders etc. No dustpan to go with the brush so I just brush it off to land on the floor.
I cut the top off a tube of mastic which as these things tend to do flies off somewhere. Mastic up the window and move onto the next. There are two of us doing this and it's a massive room.
It's only when we have finished the entire room that the pair of us realised that a lot of the crap, and the dead flies and spiders and a fair few mastic tube tops we'd let drop to the floor had entered the tea supply chain.
Because the floor had been closed off whilst we were up there (and we were outside contractors) we hadn't realised that the great big hole in the middle of the rooms floor was were they emptied the tea into huge open funnels that went to the next floor down into various containers and conveyor belts etc down in the packaging facility below.
Looking down I could see there was actual tea in the container below and I could spot quite a few mastic tops.
My boss wouldn't let me tell anyone and by the time I got down to the next floor the container had already been moved to the next stage anyway as they'd started everything back up again.
I often wonder how many complaints they got in the next few months from their loose tea drinkers about dead flies, dead spiders and mastic tube tops in their 99 tea.