The Eagle Has Fallen

[D B Campbell]

Letter to Emperor Lucius Verus:
"as many roman soldiers were killed by the Britons at the start of Hadrians reign as by the Jews"

It's not a letter to Lucius Verus; it's addressed to Marcus Aurelius.
It doesn't specify "the start of" Hadrian's reign.
It doesn't claim that "as many Roman soldiers" were killed by Britons as by Jews. (And it mentions the Jews first -- do you think that might be significant?)
With the best will in the world, I'm afraid it doesn't "clearly show that the british tribes caused a similar level of damage to the Legions as the Jews did" -- that is your (and others') interpretation.
Quite a weight of responsibility for one little Latin sentence to bear?