Late on Friday afternoon, as my bus staggered through the usual north-west London traffic, the sun was coming down, the Jewish sabbath was coming in and there were two policemen posted outside the kosher deli three minutes from my family home.
Friday's attack might have been on the Jewish community in Paris, but its consequences were felt by the community here, in France's sixth city by population, too.
Jews in London – and I'm sure elsewhere in Britain – have long felt a bit vulnerable. Every conflict between Israel and its neighbours brings a documented growth in anti-Semitic attacks. Last summer, for example, someone vandalised a charity shop in north-west London run by Norwood, a well known Jewish charity
As the years go on, we have had ever-more security guards protecting our synagogues, and tucked our Star of David necklaces a little bit further into our T-shirts. Being blamed for the actions of a far-off government we can't vote for, going to worship protected by guards, subtly doing things that don't highlight our Judaism, has become the norm.
But this is different. It is no longer the distressing – though ultimately harmless – red paint daubed on walls, nor even a brick through the window any more. British Jews know that the murderous horror that befell our French cousins this week could befall us too.
The 2008 attacks in Mumbai, when a Jewish community centre was besieged by terrorists and Rabbi Gavriel Holtzeberg and his pregnant wife Rivka were brutally murdered, showed that Jewish communities were a clear Islamist target. Indian intelligence believes the attackers were told killing a Jew was 50 times more "valuable" than killing a non-Jew.
Horrific and saddening as that attack was, it felt somewhat distant to us here in Britain. Seeing a targeted attack take place just a couple of hours away, and on somewhere as mundane as a supermarket, has brought into focus the danger faced by Jews in Britain.
A few months ago, as the Jewish high holy days approached, a friend confided that for the first time in years she didn't want her children to go to synagogue on those days. She was convinced that a synagogue would be a target for extremists, knowing it would be packed to the rafters.
Thankfully she was wrong then but her logic was worryingly accurate. The attackers in Paris targeted that supermarket in the Jewish quarter when people were preparing for the sabbath. They knew it would be full with people shopping for the traditional Friday meal, and that they could inflict most terror at that time.
I saw people doing that same shopping trip yesterday – but now it was under police protection. It's why, as Jews in Britain sat down with our families on Friday evening, we couldn't help wondering if we would be next.