It is good news that the Home Secretary Sajid Javid has announced the outlawing of the political wing of Hezbollah in the UK.

Until now, unlike its military counterpart, this wing has not been proscribed here. This is a much-needed step to ensure we are able to combat militant Islamist groups at home and advance British interests abroad. It will make it a criminal offence to be a member of Hezbollah, or to invite support for that group.

Importantly, Mr Javid’s decision had the backing of the Foreign Secretary, Jeremy Hunt, as well as from across the political aisle. Despite some equivocation in Parliament from the Labour Party’s leadership, London’s mayor Sadiq Khan urged the government to take this move in the summer so that police would at last have the power to put a stop to Hezbollah supporters parading through the capital’s streets at the annual Al Quds march. There, Hezbollah flags — emblazoned with an assault rifle — are flown openly, promoting the group and its poisonous ideology.

The spectacle of the Al Quds march is a long running source of frustration to the police. Law enforcement agencies know full well the support that movements like Hezbollah draw from such demonstrations. Hezbollah’s supporters regard this as evidence of weakness rather than liberal tolerance.

The ability of Hezbollah to hold these rallies is the result of a distinction that was made by Gordon Brown’s government in 2008, which chose to identify and ban Hezbollah’s military — but not its political — wing.

This rested on an argument that the two are either genuinely separate or that for reasons of foreign or security policy, we should at least treat them as if they were.

I was Director for the Middle East and North Africa in the Foreign Office at the time of the 2008 decision. I remember the debates very well and there were reasonable arguments on both sides.

But the distinction was always really casuistry given the unambiguous integration of both wings under a single central command structure and strategic direction. This time the Foreign Secretary’s support is notable.

As time has gone on it is less and less easy to see what benefit we obtained from treating Hezbollah’s political wing as a separate entity. Some will argue that we need to keep lines open to Hezbollah so they know our position on issues of mutual concern. But quite frankly, I have seen no evidence that conversation over sweet black tea changes the minds of any Islamist.

If you want a flavour of the eschatological goals of the Iranian Islamists with whom Hezbollah is allied, you can find Iranian commentators on the internet saying quite truthfully that the Iranian Revolution was a cultural attack on the West. And in the speeches of the top theorist of the Iranian Revolutionary Guards, Hasan Abbasi, you will find clear evidence of a level of existing hostility that will hardly be mitigated by maintaining diplomatic engagement with Hezbollah.

To be clear, Hezbollah is a terrorist organisation, responsible for profoundly destabilising parts of the Middle East. As such, it is hostile to the interests of Britain and its allies. The group was born out of Shia communities in the violent South Lebanon of the early 1980s — with Iran for a midwife. It has been responsible over the last four decades for numerous attacks; on US and French targets in Lebanon, on the Emir of Kuwait and Kuwaiti civil aviation, on Israel around the world, on the Saudi Ambassador in Washington, on senior Lebanese security officials, hostile journalists and, of course, most spectacularly, on the former Lebanese Prime Minister, Rafiq Hariri, vaporised 14 years ago by a massive bomb in downtown Beirut.

Hezbollah espouses a profoundly antisemitic, anti-Western and illiberal ideology. It supports the projection of Iranian power throughout the region, passing on its ideology and bomb-making skills to a range of groups in Iraq, Bahrain and Yemen and supporting the murderous Assad regime in Syria, all in the service of policy goals designed not in Beirut but in Tehran.

It is a massive global criminal enterprise with a hand in drug-dealing, people trafficking, financial fraud and money-laundering in Europe, the US, West Africa, Australia and South America, with an entrenched presence in the tri-border area between Argentina, Paraguay and Brazil, a hand in the turbulent politics of Venezuela and an estimated income of $1 billion a year.

Ultimately, the one thing that Hezbollah is not is twins. Its military and political wings are two parts of a single entity, with a single purpose and unified leadership. When the group’s head, Hassan Nasrallah, threatens Israel with precision-guided rockets, as he did again in his address on Ashoura last year, he is doing so as head of both wings of the movement.

Hezbollah admits the fact. Its deputy secretary-general, Naim Qassem, said in 2012: “We don’t have a military wing and a political one; we don’t have Hezbollah on one hand and the resistance party on the other... Every element of Hezbollah, from commanders to members as well as our various capabilities, is in the service of the resistance, and we have nothing but the resistance as a priority.”

There are those who will argue that since Hezbollah have ministers in the Lebanese government, we need to maintain contacts with the whole range of ministries. But Hezbollah have two ministries under the new structure, Health and Youth and Sports. That should not be a deal breaker. And if the price is the freedom by Hezbollah supporters to promote their cause in the UK because of a distinction that everyone knows is a fiction, then why would it be worth paying?

Crucially, however, Mr Javid’s decision to outlaw Hezbollah may not be the end of the matter. The very powers under the Terrorism Act 2000 that allow him to proscribe an organisation such as Hezbollah also give those placed on that register the right to mount a legal challenge and to appeal the decision. As well as directly requesting that the Home Secretary remove them from the registry of proscribed organisations, those placed on that list are able to petition an appeals commission (the POAC), and both the Home Secretary and the organisation in question can then escalate the matter to the Court of Appeal if they do not accept the commission’s decision.

So far, two organisations have had themselves removed from the register with the willing agreement of the Home Secretary. But in 2008 the Peoples’ Mujaheddin of Iran (PMOI) managed to have itself removed from the proscription list after having its case taken through the appeals commission and then through the Court of Appeal.

Even though the full ban became law as of last week, we may still see the Home Secretary’s decision facing a legal challenge. If Hezbollah and its supporters in the UK were to take this as far as the Court of Appeal, it will raise serious questions about whether our current system for proscribing terrorist groups requires further tightening.

The Home Secretary’s move against Hezbollah should be commended, not criticised. His decision will have been based on a hard calculation of our interests not just in Lebanon but in the wider Middle East, where Iran and its allies represent the most serious threat to stability – and indeed globally, where terror, intolerance, criminality and sedition should never be countered with naivety or an unwillingness to recognise the true nature of an adversary.

Sir John Jenkins is a Policy Exchange author and a former UK Ambassador to Saudi Arabia