In the end, the real troublemakers were inside the £2m ring of steel.
Barely a fifth of the 10,000 expected protesters materialised, and not even a combination of sunshine and sloganeering could generate crowds big enough to justify the massive police presence at the Liberal Democrat spring conference.
Placards were waved, flares lit, and handcuffs were slapped on one or two enthusiastic barrier climbers by officers drafted in from across Yorkshire and Derbyshire. Each delegate was jeered as they climbed the steps to Sheffield City Hall, encircled by eight-foot fences.
Inside, perhaps emboldened by the protests, they let rip. Activists, MPs and grandees tore into the coalition's NHS reforms, reasserting their authority over a party leadership that many believe moved into high office without some of the principles that made the Lib Dems different.
Nick Clegg, the party leader and Deputy Prime Minister, still struggling to square his two roles, will today signal that he has heard the message and spell out who he is in politics to help. Reviving his concept of Alarm Clock Britons who "want to get up and get on", he will attack both Labour and his Tory coalition partners who claim to be on the side of people who work hard to make ends meet "but always let them down".
"They have been failed for generations," Mr Clegg will say. "Failed by the tired tribalism of left and right. But we are not on the left and we are not on the right. We have our own label: Liberal."
The attack on the Conservative right, as well as Labour, will resonate in a city with a deep hatred of the Tories since the miners' strikes of the 1980s. Some of the biggest applause yesterday was saved for Tim Farron, the party president, condemning Margaret Thatcher's "avoidable human misery caused by a government that didn't understand the North and cared about it less". He also said David Cameron was "wrong" in claiming multiculturalism had failed and in advocating the privatisation of public services, including the NHS.
Lib Dem ministers now have a mandate to seek changes to Andrew Lansley's health reforms, which have exposed the most significant tensions in the coalition yet. The party leadership accepted a conference motion deploring the "damaging and unjustified market-based approach" being taken by the coalition.
Lib Dems are particularly aggrieved that the reforms were not party policy or part of the coalition agreement, which "called for an end to large-scale top-down reorganisations". Concerns were raised about the lack of accountability in the plans to hand GPs control of £80bn in health spending and fears it will open the door to privatisation "by the back door".
The former Cabinet minister Baroness Shirley Williams cautioned that the "accountability proposals of the new structures are lousy", and private firms would "cherry pick" profitable services. Andrew George, MP for St Ives, said that, without a rethink, the Lib Dems risked becoming "architects of the NHS's demise". He added: "Joining the coalition does not mean we have to turn into forelock-tugging automatons."
Downing Street has belatedly woken up to the problems posed by the NHS overhaul, and aides to Mr Clegg are understood to be furious at the pace and scale of the changes. With rebellion in the air, the conference also passed a motion stating that changes to the Disability Living Allowance "may amount to a breach of the UK obligations under Human Rights Conventions". In a further sign of defiance, the party adopted a policy to raise the age of criminal responsibility from 10 to 14. Another motion will reject an electoral pact with the Tories and insist they fight the next election with no preference for future coalition partners.
For many, though, other elections are more pressing. On 5 May, hundreds of Lib Dems will defend seats in key councils, including Sheffield, Hull and York, and in the Welsh Assembly and Scottish Parliament. Strategists are resigned to losing seats, and control of metropolitan authorities.
For Lib Dem councillors fearful of a pasting at the ballot box, there was little in Sheffield to alleviate their anxiety. Speaking at a rally on Friday night, Mr Farron told delegates that winning the Alternative Vote referendum on 5 May was "even more important" than the local elections, and must take priority. "It's game-changing, earth-shatteringly significant," he said.
It will be tough. In an opinion poll for The Independent on Sunday, the No campaign has a three-point lead at 37 per cent, with 34 per cent saying they back electoral reform. Last month, the Yes campaign was on 40 per cent with a 10-point lead.
The No camp is increasingly confident that Clegg's association with AV will work to its advantage and will release leaflets featuring the Lib Dem leader signing his infamous – and broken – pledge to abolish tuition fees, along with other "broken promises". Matthew Elliott, the director of the No to AV campaign, said: "The polls clearly demonstrating the £250m cost of AV and the spectre of President Clegg are having an impact on voters."
Yes campaigners are now facing a battle on two fronts. Some supporters of proportional representation are also encouraging voters to defeat AV. Writing in the IoS today, the former SDP leader Lord Owen says the coalition should have offered a three-way referendum, on first past the post, AV and PR. "AV is no more than the 'miserable little compromise' Nick Clegg described it as," he claims.
But on a crisp Sheffield morning yesterday, the subject of AV left many protesters cold. Carrie McKenzie, recently made redundant from a job in the voluntary sector, voted for Mr Clegg in May, but joined the protest yesterday. "It was the worst tactical vote to prevent the Tories from getting in and because of Clegg's promise on tuition fees. I would rather see care homes for the elderly and the NHS protected than have a change to the voting system."
Anger over tuition fees remains. Vince Cable, the Business Secretary, admitted yesterday he was worried about the number of universities wanting to charge the maximum £9,000 tuition fees. Conceding failures in selling the policy, he added: "A lot of energy was spent talking to our coalition partners and not enough energy was spent talking to you [Lib Dem members] and the public."
The prospect of marauding protesters hijacking the conference had built all week, even leading to fanciful claims of a kidnap plot against Mr Clegg. In the event, the protest failed to live up to either the predicted numbers or the level of anger.
The placards ranged from the straightforward "Tory scum" to the downright rude: "Lib Dems – putting the N in CUTS." Another sign held aloft seemed mindful of the apathy. "If you're not angry yet, you're not paying attention." Many Lib Dem activists are also quietly fuming, and will hope after this weekend that Mr Clegg takes note.Reuse content