A lot of people had a good laugh when Lord Mandelson was covered in green custard by the anti-Heathrow protestor Leila Deen.

At least it wasn't mushy peas.

Ms Deen said her protest was”non-violent” which, even with benign slime, seems to be a new definition.

It's nothing new.

People feel strongly about something. They think the system is not working and decisions are pushed through by the "establishment" without fair debate - or are not what people want.

So they take to direct action. For publicity, or to create a nuisance and cause disruption, or even to stop the work (Swampy - where are you now?) At the opposite extreme to Ms Deen's green custard, a group of gangsters calling themselves the Real IRA have killed two soldiers in Northern Ireland.

So what is acceptable? Shooting British soldiers is obviously wrong and was even so when Messrs McGuinness and Adams were helping to run the IRA.

But so is splashing custard over a Minister.

Truly non-violent actions, carried out openly and honestly, cannot be morally challenged.

But the real danger of harmless symbolic actions like chucking custard at unelected Ministers, or bags of flour into the House of Commons, is that they are another excuse for the powers-that-be to ratchet up the security level.

And so Parliament is slowly turned into a fortress. Politicians are kept away from the people they work for.

The Commons have just sent the Political Parties and Elections Bill up to the Lords "to which they request our agreement".

One thing it does in the interests of security is to allow candidates at General Elections to hide where they live from the voters (something MPs have already agreed over publishing their expense claims for their second homes).

I find this extraordinary. As an active politician and representative I am in the phone book and my address is on various websites and available via the council - and indeed I stick it on leaflets.

Perhaps I'm not important enough for anyone to want to cover me with custard.

But we either have an open democracy or we don't and if we do politicians do not hide.