Politicians and police in Britain have spoken of "heightened concern" in Jewish communities following the terror attacks in France that included the killing of four men at a kosher supermarket. So what has been the impact on people living and working in Jewish areas, such as London's Golders Green?
"An attack in our community is inevitable."
Israel Morgenstern is bracing himself for a terror attack aimed at the Jewish community in Britain. "It's going to come. It all depends how and where."
Mr Morgenstern, 37, who lives in Golders Green but is originally from Israel, is married with three children, and says he has a weight on his mind whenever he sends them off to school.
While he is talking, he points out three police cars which pass by, and also says that he welcomes local patrols conducted by the Community Security Trust (CST), a Jewish security charity.
However, he says that he does not know "how much they would be able to help" in the event of an attack. "Maybe, just maybe they would alert the police two minutes earlier.
"I like it in this country, I prefer it to Israel. We want to relax here, but we can't right now."'On edge'
Lord Sacks, former chief rabbi of the United Hebrew Congregations of the Commonwealth, has told the BBC that anxiety levels among British Jews are at an "all-time high" in his lifetime.
However, he adds that "the most recent survey shows that the overwhelming number of Jews in Britain feel safe here. It remains one of the most tolerant societies on earth".
The threat has been a background noise for many years, he says. "We are used to it, we are well prepared. This is well under control."
Along with the visible increased police presence in Jewish areas of London, "internally our security level has risen", he says.
At one of the area's largest kosher supermarkets, all appears to be business as usual. But its manager Chuny Rokach says that, since the Paris attacks, anxious customers have been phoning and emailing him to ask what security measures the shop has in place.
"We've trained our staff on what to do if there is an incident - how to communicate, where the exits are," he says.
"They have radios, and we've checked our CCTV to make sure it's effective. People are still shopping, but our customers are definitely on edge. "
Mr Rokach is in daily contact with the CST, but says he wants to see more police actually walking the beat, not just driving up and down the main road.
"The police haven't been in touch to talk to us about security. We haven't had any issues, but obviously it's a concern.Continue reading the main story
There are attacks in Jerusalem, but I was more scared in London”End QuoteIsraeli tourist
"You do see some extra patrols on Saturdays and Sundays, but we've communicated through the CST that we'd like to see a more visible police presence in the area."Party security
The authorities say they are listening to concerns. On Friday, Met Police assistant commissioner Mark Rowley, the national policing lead for counter-terrorism, said a security review was under way, and that police were holding talks about providing "more patrols in key areas".
It is a measure that has been welcomed by leaders in the Jewish community, while some individuals are also taking their own steps in order to feel safe.
Frances Bronzite, 64, is visiting Golders Green from her home in Redbridge, Essex, to buy supplies for her son's engagement party.
She consulted with the CST about the party, and was advised that they should arrange to have security present.
"I told my son, and I thought he'd laugh, but he said, 'No mum, they're right,'" she says.
"It's a party at his fiancee's house for about 200 people. They told us we should have security on the door.
"That never would have occurred to us before."
Mrs Bronzite says it is not just the threat of Islamist extremism that worries her, but also what she sees as a rise in right-wing anti-Semitism.
"I haven't changed my behaviour. Why should I? I still go about life as normal. We're British, born and bred.
"But I think we have to be very wary and very observant. I haven't felt this worried before."
It is a view echoed by two women who stop outside a Jewish bakery to chat. They are happy to give their opinion, but do not want to give their name or a photograph for fear of being "targeted".
The younger of the two is visiting from Israel.
"Of course there are attacks in Jerusalem, but I was more scared in London," she says. "I was scared to go to the kosher supermarket.
"Personally, I feel people here should be moving to Israel."
Her companion is more stoical, however.
"I've lived here for 40 years," she says. "Of course we're worried after seeing what happened in Paris, but you still have to go shopping and do things.
"The way I deal with it is to not think about it. If I let myself think about it, of course I will be scared. But you have to get on with life."