Peter Mason endorses this Fathom Journal report: https://fathomjournal.org/wp-content/uploads/2019/03/Institutionally-Antisemitic-Report-FINAL-6.pdf
On page 2, Mason fully endorses its content:
Page 18 of the same Fathom Journal report also helpfully gives examples of Anti-Semitism through the ages, including the 'well-poisoning' trope:
In a separate later article written by Mason himself (https://www.thejc.com/comment/opinion/starmer-s-response-to-the-ehrc-report-will-be-a-major-turning-point-in-the-history-of-labour-antisemitism-1.501241), he goes on to use this very same antisemitic trope to describe 'hard left' activists, some of whom are certainly Jewish, who joined Labour in 2015:
With just the quickest of searches, I found two 'hard left' Jewish activists who rejoined Labour in 2015. I'm sure there must be more.
(https://twitter.com/JustJewsUK/status/1168467580409077760)
(https://twitter.com/TheBirmingham6/status/988855102223147008)
(https://twitter.com/TheBirmingham6/status/1330513201667186691).