What ethnic origin's were connected to Diamond cutters in London (east end I bel

Question:

What ethnic origin's were connected to Diamond cutters in London (east end I believe)?

I am trying to trace my Grandfathers roots in the east end of London. I cannot find any record of him on any census's.
His surname was Lambert.
My aunt informed me that her father said that his family had been diamond cutters, yet all I know him to have been was a rag and bone man.
Any help on the matter would be most grateful for these family history sites are such a rip off.

Best Answer - Chosen by Asker: Hatton Garden being the largest area for the Jewish diamond cutters as I am led to believe. Just down the road was also the Jewish cloth stalls. (Now mainly African owned)
You could try to see if there are any records of shop owners with your grandfathers name around Hatton Garden.
I hope you got lots of time on your hands!