An adviser to the United Kingdom’s Home Office has published a 12-page guide recommending that churches keep bouncers outside their doors during services to protect from violent attacks by extremists.

“Make sure that someone is stood by the door before, during and after the service, whilst the congregation is present,” the guide says. The person should be ready to lock the doors if he or she sees an attacker approaching.

Churches are also advised to create surveillance systems and alarms, and to train parishioners about what to do if an attack occurs or if they see a suspicious character.

The advice comes one month after the death of Jacques Hamel, a French priest whose throat was slit during Mass by two Islamic radicals.

The guide is the work of Nick Tolson, an expert on church security who provides advice to the Home Office, the department in charge of U.K. internal security. The Home Office has already promised to spend $3.14 million helping churches improve security.

Tolson warned that smaller churches, like the one Hamel presided over, were the most likely to be attacked in the future.

“It won’t be Westminister Abbey or St Paul’s [Cathedral], it will be a little church in Bolton or Birmingham,” Tolson said, according to The Telegraph. “It’s the small churches, just like the one in France. You can walk into any church on a Sunday morning and it probably won’t be a gun, it will be a knife.”

Some British clergy claim they have been warned to avoid wearing clerical collars in public, lest they be targeted for violence, but Tolson said that currently isn’t warranted.

“There’s zero evidence that wearing collars is any risk,” he said.