Mohammad Naseem, chairman of the Central Mosque in Birmingham, one of Britain’s largest, is 89. Born under British colonialism, he served as a doctor in the British Army and came here in 1959. He said he understands why Muslims are uneasy and defensive these days.

“When you go outside the boundary, you’re not sure where you stand,” he said. He said he sees the new fashion for Islamic head covering and veils less as religious than as a reaction to outside pressure. “When you’re being downgraded or threatened,” he said, “there is a natural reaction to hit back and say, ‘This is my identity.’ ”

In London, anti-Muslim episodes rose from 318 in 2011 and 336 in 2012 to 500 by mid-November in 2013, the police reported. The Greater Manchester Police recorded 130 offenses in 2013 compared with 75 in 2012. The West Midlands Police force, which covers Birmingham, reported in response to a freedom of information act request that there were 26 anti-Islamic hate crimes in 2011, 21 in 2012 and 29 through October 2013.

Tell MAMA, an advocacy group that monitors anti-Muslim episodes nationwide (MAMA stands for “measuring anti-Muslim attacks), said that such episodes had almost doubled in a year, with a surge after the Rigby killing, to nearly 1,000 cases. But the group does not separate online attacks from physical ones.

It is not clear how the current tensions will affect what some analysts say has been a slow but gradual trend of greater racial understanding in Britain, though periodically interrupted by racial and ethnic eruptions of hostility. News media attention to immigration from within the European Union has also helped dilute the focus on Muslims.

“Islamophobia intensifies after big events like 9/11, 7/7 and the Lee Rigby murder, and anti-Muslim hate crimes spike,” said Humayun Ansari, a professor of Islamic history at Royal Holloway, University of London, referring to the July 7, 2005, bomb attacks in London. “Then it actually fades away and dies down to a much lower level of intensity.”