‘Hushed-Up’ Blitz Tragedy Remembered

I wonder if anybody can confirm the story of another incident not so far away from this one?
Just south of the Angel tube station apparently another shelter had a near miss, which shattered the culvert of an underground river ( The Lea ?) flooding the shelter and causing many casualties.
I was told this version by cleaning ladies some years back, who worked in the City University Dame Alice Owen building which adjoined the apparent site.

bittery sad event…covered well in the superb Blitz Then & Now book….certainly stuck in my mind….used those steps when I was a Stude at QMC on Mile End Road….the other was the tragic Fw190 bombing of the school the now & then photos are moving

At the time of the Blitz I was a schoolboy living in London. Because it being hushed-up we did not know much about this Tragedy we heard of it through the rumours that were flying about at time. Today there is a small plaque to commemorate this Tragedy.