At 6:00pm I arrive in Parliament Square for what is possibly the first illegal carol service of modern times. Under Section 132 of the Serious and Organised Crimes and Police Act 2005, anyone taking part may, if found guilty, be liable to a fine of up to £2,500 or up to 51 weeks in prison. Welcome to Tony Blair's Britain.

The threat to free speech doesn't seem to have put us off, however; there's peace and goodwill in abundance. We take a song sheet, and a rather ropy white candle with a home-made cardboard shield to stop the hot wax dripping on our hands. The crowd launches into O Come All Ye Faithful, followed by Away In A Manger and The Little Drummer Boy. My friend Gareth standing next to me comments that as a veteran of organising singalongs at political events, the latter is not always an easy choice for keeping amateur groups singing together in the same key!

Still, we gather pace through The Twelve Days of Christmas, Deck The Halls, Good King Wenceslas and a host of well-known Christmas favourites. As our candles sputter and blow out, our neighbours use theirs to re-light them for us. It's all completely peaceful; no placards, no violence, just real friendship and a shared view that free speech is something that shouldn't be thrown away lightly.

Towards the end, there's a minute's silence; then veteran protestor Brian Haw - whose longstanding demonstration outside Parliament the Act was brought in to silence, but which the courts have ruled is the only one not affected by the new law - delivers some closing thoughts in typical Brian style.

The police have been notable by their absence; there are normally far more of them around Parliament than there are tonight. Clearly they've decided they'd look utterly foolish trying to enforce Blair's new law, and arresting a bunch of well-behaved citizens (including at least one member of the House of Lords) for simply singing Peace on Earth and Goodwill to all Men.

Note: the event was organised by Tim Ireland of Bloggerheads and raised £300 for Medical Aid for Iraqi Children.