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Four people lost their lives and dozens were injured at the hands of a home-grown terrorist . But after an atrocity we often see two other possible casualties – freedom and privacy.

Khalid Masood used the encrypted message system WhatsApp on his phone before the attack.

Home Secretary Amber Rudd then demanded WhatsApp end its encryption, a crazy move that would allow criminals and foreign governments to hack the messages.

The security services didn’t join her call. Probably because they know how to do it anyway.

Over in the US, it was claimed our spies were involved in tapping Trump’s team in the run-up to the election. GCHQ ’s chief described the claim as “ridiculous”.

But tapping politicians isn’t new.

When I was a striking seaman, I was tapped by the intelligence agencies. People suspected they were also tapping MPs’ phones. So PM Harold Wilson introduced the Wilson Doctrine in 1966.

It ruled that MPs’ communications must not be intercepted by the police and security ­services. If an MP was tapped, the PM would have to tell Parliament. But in 2005, when I was Deputy PM, I was told by Tony Blair an MP had been tapped in the past without Parliament being told.

I asked him who it was and he told me the MP was the Rev Ian Paisley.

Downing Street had been told by the Interception of Communications Commissioner, who wanted to name Paisley.

(Image: PA)

Tony asked me to discuss the Wilson Doctrine with the Speaker of the House of Commons.

I never told him that an MP had been tapped or that it was Paisley.

Parliament was not informed and Paisley went on to become First Minister of Northern Ireland.

I can only think that as the peace process was still a concern, mentioning the fact a leading loyalist politician had been tapped by Britain’s security services in the past would not have helped.

Any tap must be approved in writing by a minister, ­usually the Home Secretary. Some are vital. After the Omagh bomb that killed 29 people in 1998, I was asked to sign warrants giving permission to tap the phones of the suspects.

I agreed but later discovered the spies had already been doing it and had not even told the police.

It’s illegal to secure information about American citizens without proper authority. But there’s ­nothing to stop our security ­services doing it for the US.

We now know there has been close co-operation between GCHQ and its US counterpart, the National Security Agency for years.

(Image: PETER MUHLY/AFP/Getty Images)

In ­Cabinet I was concerned about this relationship, especially when it ­became clear the Public Accounts Committee failed to agree GCHQ’s accounts.

The Thatcher Government had cut its financial support of GCHQ by £100million. But we later discovered the US paid at least that amount to GCHQ to influence our ­intelligence gathering.

It doesn’t stop there. This government introduced a “Snooper’s ­Charter” – the Investigatory Powers Act, which was the idea of Theresa May when she was Home Secretary.

It requires web and phone firms to store everyone’s browsing history for a year and give the police, security services and official agencies access to the data.

Now May is threatening the EU that if it doesn’t give her the best Brexit deal, it will lose access to our security information.

The challenge as a minister is to balance national security against the freedoms we enjoy. But this government seems determined to ensure Big Brother is not only watching you, he’s monitoring your calls, emails and texts.