Westminster has a rich vocabulary of euphemisms designed to avoid any politician having to say that an MP has lied: terminological inexactitude, porkie pies, being economical with the actualité. They are after all, “honourable members”.

It was always assumed in parliament that if any MP was proven to have lied he or she would have to resign immediately. This was why the very word was forbidden. In the 19th century, such an accusation could have led to a duel.

But we live in different times. You wonder if MPs will still be foregoing the “L” word in future: it seems kind of pointless when members so clearly lack honour that they fail to resign even after being exposed as bare-faced liars.

We now have an MP, the Right Honourable Alistair Carmichael, who has been described in a court of law no less as having told a “blatant lie”. The evidence given by the former Secretary of State, was in the judges’ ruling, “unreliable and lacked candour” ... “at best disingenuous at worst evasive and self-serving”. The law Lords didn't mince words.

This isn't so much reputational damage, as reputational obliteration. You couldn't help thinking that Lord Matthews and Lady Paton were going as far as they reasonably could in a court judgement to make Carmichael's future as a politician untenable, even though they exonerated him under the Representation of the People's Act.

I won’t go into the legal technicalities, but he was cleared essentially because it couldn't be proved by the petitioners “beyond reasonable doubt” that the lie he uttered in the Channel 4 interview in question specifically related to his own character and wasn't merely a “political lie” which did not relate to any claim about his personal honesty.

No – I don't fully understand the distinction either. But part of me is rather relieved that the court did not uphold the petition, however much I sympathise with the Orkney petitioners. It would have been a disturbing precedent for judges to overturn the result of a democratic election, even if one of the candidates is an acknowledged scoundrel.

It is for voters to decide who they wish to represent them in parliament. I suspect this weighed heavily on the judges in the Orkney case and made them disinclined to rule that the May election in Orkney and Shetland was invalid.

Had there been a right of recall – as the Liberal Democrat MP himself had been advocating – then there would have been a means to displace him through democratic means. Again, a truly honourable member might have offered to put himself up for recall.

Of course, the Orkney petitioners' claim was that Carmichael's lies had allowed him to steal the election. If he had told the truth about authorising the leak of a civil service memo alleging that Nicola Sturgeon wanted David Cameron to win the general election, the Orkney petitioners say he would never have won the seat.

Well, that is understandable, but it doesn't necessarily follow. The judges made clear that, like it or not, politicians do frequently leak documents, both to flatter themselves and to damage their enemies, and voters are not so naïve that they don't understand this.

The former PM, Gordon Brown, was one of the most prodigious leakers in parliamentary history, before and after he became Chancellor. In 2013, his disgraced former spin-doctor, Damian McBride, freely admitted leaking Budget secrets with his boss's full knowledge and “encouragement”.

Of course, arguably it was not Carmichael's leak as such, but his lying about it, that was the greater offence. But if every time there is a leak, a lie or an evasive answer from a politician, we end up with a court case, democracy would become impossible.

The truth is that sometimes politicians have to lie. For example, James Callaghan, when he was Chancellor in 1967, lied about his intention to devalue the pound. If he had admitted that this was what was planned, it could have caused financial chaos and a run on sterling.

Governments lie their heads off about war and foreign policy. When the former Tory minister, William Waldegrave, admitted this to a commons committee in 1994 he caused a huge row, and calls for him to resign. But the minister for open government, as Waldegrave was at the time, was only telling the truth about what might be called ‘lying in state'.

And it is even legitimate, in my opinion, for MPs to lie about their personal circumstances in order to protect their family. Tony Blair did this to protect one of his daughters from press scrutiny when she had psychological difficulties. No parent should have to put honesty above their children's welfare.

However, it may be that the Orkney case does actually change ministerial behaviour for the better. Alistair Carmichael is the first cabinet minister, as was, in half a century to be held to account for the black arts of unattributable briefing. You have to go back to 1947, when the Labour Chancellor, Hugh Dalton, resigned after inadvertently leaking a few lines of his Budget speech a few hours before it was delivered.

Ministers in future will certainly think twice before authorising leaks in case they are asked to account for their actions in court. Civil servants, who in many government departments have acted as willing conduits, will certainly be citing this case when next they say: “Minister, do you think this course of action is wise?”

The Orkney petitioners may have lost, but they did establish beyond reasonable doubt that there was a case to answer; that the kind of activities in which Carmichael was engaged could lead to serious consequences. At the start of the legal process few in the legal profession believed the petitioners had the remotest chance. I certainly didn't.

After all, Carmichael had not told a lie or said anything damaging about the other candidates in the constituency where he was standing. How then could his involvement in a newspaper story about Nicola Sturgeon allegedly saying she wanted David Cameron to win the general election have any bearing in the local contest in Orkney and Shetland, which is key to an action under the ROPA?

But the rather brilliant QC for the petitioners, Jonathan Mitchell, established – as I understand it - that actions Carmichael took as Secretary of State for Scotland, and statements made about himself rather than other candidates, could be seen to affect the outcome of this local election. Lady Paton was certainly persuaded of this.

This is potentially political dynamite. When Tony Blair famously said, after the original cash for access scandal in 1998, that “people know I am a pretty straight kind of guy” he could have been laying himself wide open for a legal action if it was subsequently discovered that his had lied.

Critics of the former PM have been looking to have him held to account in the International Criminal Court for war crimes because of his lack of candour over the Iraq war. Perhaps they should have been looking for a case under the Representation of the People’s Act over the conduct of his election in Sedgefield.