"You filthy Muslim dogs. You will be torched this Friday. Many Muslim pigs will burn," the hand-scrawled note reads.
At a recently vandalised mosque in the east of Britain's capital, a shocked 65-year-old Siddique Ali handles one example of hate mail targeting British Muslims after the deadly bomb attacks on London's transport system on 7 July.
"We are afraid," said Ali, a member of the committee which runs the mosque.
"These people are giving us warnings. But if they came in front of us we could give a reply or try to understand, but they are not coming."
Britain is home to 1.6 million Muslims, just under 3% of the population.
The vast majority hail from the Indian subcontinent rather than the Middle East.
Community relations in multicultural Britain have generally been peaceful, although tensions between different ethnic groups occasionally flare into violence such as summer 2001's race riots in the northern towns of Bradford, Oldham and Burnley.
British Muslims say they suffered increased abuse after the 11 September attacks on New York later that year, but that those tensions had largely dissipated prior to the London blasts.
Two days after the 7 July bombings, however, vandals smashed about 20 windows at the front of the Mazahirul Uloom Education and Cultural Institution, a bright blue mosque in the east London district of Stepney Green.
London's Central Mosque in
Regents Park during Friday prayer
Prayer leader Saleh Ahmed surveyed the damage alongside Ali.
"I was sleeping upstairs and late at night, about three o'clock, I heard a banging sound," Ahmed said. "I came down and found these broken windows and glass all over the floor."
Crime experts say the figure of 269 hate crimes since 7 July is an underestimate as many offences are not reported.
Unofficial estimates range up to 20 times higher.
The Muslim Safety Forum lists murder, arson, assaults and bomb threats among the incidents.
In one case reported in south London, an imam was attacked and beaten unconscious as he cycled to afternoon prayers .
Less violent episodes include reports of bus drivers refusing entry to Muslim women wearing the hijab, or headscarves, racist graffiti and bacon smeared on a mosque entrance in Wales.
Concerns in the Muslim community are such that the chairman of the Council of Mosques and Imams, Zaki Badawi, has suggested that Muslim women could stop wearing hijabs to avoid abuse.
Muslim women were told to better
not wear Hijab to avoid abuse
But the Assembly for the Protection of the Hijab, a Muslim women's group, rejected the idea and said wearing the hijab was a duty.
The Muslim Safety Forum fears July's attacks could lead to widespread discrimination against Muslims in Britain.
But in the multi-ethnic London neighbourhood of Brixton, a few minutes walk from where police mistook a Brazilian man for a bombing suspect and shot him dead, Muslim women said they had yet to suffer discrimination because of the bomb attacks.
"Where there are more white people maybe there is (a problem)," 29-year-old grocer Makka Adams said. "It is so mixed here I do not feel different."
"But I do not know what will happen tomorrow."