MI5 have played a key role in saving lives in Northern Ireland

It was Her Majesty’s first visit to the agency at its headquarters in Thames House in central London. She thanked MI5 on behalf of the nation.

The Queen was referring to MI5’s work across the UK and she was right to do so. It has been a vital element in the fight against terrorism in recent years, and in multiple other threats in previous decades, including during World War II.

But there is a part of the UK where MI5’s work is particularly important — Northern Ireland.

Intelligence is one of the last lines of defence against dissident republican terrorism.

Those terrorists, plotting murder and mayhem as you read this column, are relatively small in number but they are accomplished in their terrorism.

It is hard to convict such killers, because they are highly skilled in covering their tracks. That is one reason why the conviction rate in dissident murders is so low.

To observe that failure is not to criticise the police, in their heroic anti terrorism work, or the legal system, which is full of admirable people who are doing their utmost to administer justice. It is, instead, a reflection of the great difficulty that any nation that adheres to strict human rights standards has when stopping fanatical ideological murderers.

Therefore, intelligence is the last line of defence against those who take human life.

Nationalist politicians have criticised the MI5 base in Co Down, and implied that it is a sinister place, staffed by spooks. At the same time, ‘human rights’ activists are doing what they can to diminish and constrain the use of informers, who are so important to thwarting illegal violence.

Let us hope such thinking does not prevail. Many lives would be lost if our intelligence capacity against dissidents was in any way diminished.