You’re right about Halevy being right, which means Dalrymple’s chronology is off. The changes began happening in the late 18th c.—Wilberforce’s campaign against slavery, the prison reform movement, founding of missionary societies, etc.
It’s interesting that an earlier poster said his wife told him that reading Jane Austen made him more polite but less sincere. Yeats’ brother told him the same thing, after he’d read Castiglione’s The Courtier. Which suggests the stiff upper lip values go back to the Renaissance, which means they come from Cicero and Stoicism.
The English managed to meld this aristocratic, non-Christian outlook w/ Evangelical/Methodist piety and reforming zeal. That’s quite an achievement.
As in his take on the London riots, Dalrymple manages to ignores the effect of mass immigration—tho’ the corruption of English manners and morals is probably as much a cause as well as a consequence of the invasion.
I don't think it's a cause or a consequence but a parallel development. British morals started to get corrupted in the 70s, post the flower-power revolution and immigrants were only really visible in the late 70s.
And it depends on the immigrants -- Moslem immigrants from Pakistan tend to be the most criminal, along with Jamaicans. This is because those immigrants were mostly uneducated, low-skilled labor to work in mills etc. Once those shut they were not skilled enough to rise.
On the contrary Hindu and Sikh and Indian Christian immigrants tend to have the lowest crime-rates because the communities that migrated were shop-keepers or businessmen or doctors or engineers.
Bangladeshis and non-Jamaican Caribbean folks are somewhere in-between -- they tend to be low-skilled but not the absolute no-skills as Pakis or as heavily infiltrated by gangs as the Jamaicans.
The Russians and Ukrainians in the UK unfortunately seem to have been infiltrated by gangs -- there are many good, honest folk among them, but the gangs have slipped in and given all a bad name.