The closer we get to the election, the louder the question resonates: what have Liberal Democrats brought to government? In all the compromises and stresses of coalition, has our difference made it all worthwhile?

In the area of civil liberties, so important to us as a party, the answer must be a resounding ‘yes’. Of course not all the coalition battles around freedom have taken place in public, but they have been fiercely fought nonetheless- sustained, difficult struggles against the Tories and parts of the Whitehall machine, to keep our country loyal to its most enduring values in the face of terrorism and risk.

The appetite of the securocrats for more and more surveillance, more and more powers, ever-greater intrusion into everyday lives, appears at times to be almost without limit. As Director of Public Prosecutions during a period of intense terrorist threats following 9/11 and our tragically misconceived invasion of Iraq, I saw at first hand the extent to which politicians, even government ministers, would abdicate their responsibilities in this area. Too often they bowed down and failed to fulfill their most important role: to scutinise.

More than once in policy meetings I heard Tony Blair say: “if the security agencies want it, they must have it- they’re the experts’. The result, as we recall only too well, was Labour’s uncritical push for 90 days pre-charge detention, and its Orwellian scheme for identity cards and a giant state-controlled database of everyone’s communications. If the agencies made a case, the last government was persuaded. Any opposition, or even the suggestion that evidence was required to justify any dilution in freedom, was portrayed as a show of weakness in the face of Al Qaeda.

Of course, the opposite was true. For there was never anything courageous about a populist rush to dismantle our constitution, about chasing easy headlines or surrendering liberty to fear. Real political bravery, then as now, involves principal and tenacity in the face of threat. It involves recognising the value of what we’re trying to protect, and not giving it all up at the first sign of danger. It involves a government scrutinising the demands of the securocrats with rigour, balancing their policy claims with the freedoms so long associated with these islands- and when the spooks are wrong it means having the guts to say ‘no’.

On these tests, Liberal Democrats in government have succeeded from day one. In the early period of coalition we were instrumental in repealing some of Labour’s worst legislation, from restrictions on taking photographs in public, to the abolition of open-ended control orders. It was us who fought to bring pre-charge periods of detention back to 14 days, and we insisted in changes to the secret justice proposals, taking powers from ministers to insist that courts go into secret session and returning the decision to its proper place, with the judges.

More recently, Nick Clegg made it clear to the Home Office that there would be no snoopers’ charter while we are in government, a principled stand to make us all proud.

This resistance to excess makes us stronger, not weaker. And, so, too, does the new Counter Terrorism Bill, coming before the Commons this week.

Frankly, we all know what would be in this legislation if the Tories were governing alone. If it were not for coalition we would have: archaic prosecutions for treason, offering spurious glory to young terrorists who should be facing trials for murder and rape, and for modern war crimes like kidnap and torture; statelessness for young British citizens, as though other countries would somehow allow our own home-grown terrorists to roam their streets at will; and the snoopers’ charter, an insult to the whole notion of a freeborn people. As I have written before- all juvenile solutions to grown up problems.

However, mature government also means having the courage to accept policy change where it offers our people greater protection and continuing respect for civil liberties, where the balance is properly met by a combination of the agencies’ desires and thoughtful rights-based reform. Government is a two way street: you don’t protect freedom by being naïve.

So again, Liberal Democrats have fought those battles. And the result is a Counter Terrorism Bill that is realistic, offering both security and the protection of British freedoms. We acknowledge that in a world where terror is increasingly globalized, where young Britons can travel more or less at will between war-zones, their relocation as part of a TPIM may be a proportionate response to new threats.

But Nick Clegg has also insisted that in future the test for imposing a TPIM must be higher, so that rather than just acting on the Home Secretary’s suspicions, a court must now be satisfied on the balance of probabilities that an individual has been involved in terrorism. And we have also insisted that the definition of involvement in terrorism must be tighter, so that it focuses on those who are more directly participating in dangerous criminal activity. This is a victory for liberal values: we are protecting our people, but with measures more respectful of basic legal principles, more loyal to due process.

Similarly, while rightly rejecting a Tory Home Secretary’s more extreme demands for a surveillance society, Liberal Democrats understand the need for a scheme that allows the police, where investigations take place, to tie particular communications to particular devices. Again, this provision keeps both the public, and its liberties, safe. It marks out the real strength that liberal values have brought to coalition.

In the aftermath of terrible mass murder on the London transport system on 7 July 2005, Tony Blair memorably declared that many of our civil liberties ‘belong to another age’. As Nick Clegg has made clear, Liberal Democrats yield to no one in our determination to protect the British people from terrorist violence. But we also understand that to pretend to guard our country at the expense of our freedoms brings a false and fraudulent cost, and one that should not be paid. For Liberal Democrats, civil liberties belong to every age.

* Lord Ken Macdonald is a former Director of Public Prosecutions and Liberal Democrat member of the House of Lords