Colonel Richard Kemp is a former senior UK intelligence official and former chairman of the Cobra Intelligence Group who briefed the British government on secret intelligence.

Speaking with BBC Newsnight this week, Kemp said that the 23,000 jihadists MI5 officials have publicly admitted are living in the UK "may be the tip of the iceberg":

MI5 figure of 23,000 suspects who pose terrorist threat is probably "the tip of the iceberg" - former intelligence adviser tells #newsnight pic.twitter.com/8rw0LBzf33 — BBC Newsnight (@BBCNewsnight) June 26, 2017

The 23,000 number was reported in the days following the Manchester arena attack last month that left 22 victims dead and 250 injured.

Latest Developments on the Ariana Grande Manchester Concert Bombing Investigation https://t.co/4LmWPi4YpM #HomelandSecurity via @pjmedia_com — Patrick Poole (@pspoole) May 25, 2017

The Times reported:

Intelligence officers have identified 23,000 jihadist extremists living in Britain as potential terrorist attackers, it emerged yesterday. The scale of the challenge facing the police and security services was disclosed by Whitehall sources after criticism that multiple opportunities to stop the Manchester bomber had been missed. About 3,000 people from the total group are judged to pose a threat and are under investigation or active monitoring in 500 operations being run by police and intelligence services. The 20,000 others have featured in previous inquiries and are categorised as posing a “residual risk”.

Those MI5 figures were confirmed by UK Home Secretary Amber Rudd the following day on Andrew Marr's BBC show.

Amber Rudd confirms 23,000 terror suspects on MI5 radar inc 3,000 on 'top list' #Marr — Alan Travis (@alantravis40) May 28, 2017

But Kemp's stunning admission that these figures on the number of jihadists may be vastly understated lends evidence to the claim that the extent of the threat in the UK may exceed authorities' ability to deal with it.

The pace of terror attacks in the UK this year has been staggering.

AC Rowley: 3 attacks in 10 weeks, 5 plots foiled since March & 18 thwarted since 2013, tempo of threat unprecedented https://t.co/2vRtlb9LBV pic.twitter.com/5n7YnZHmvS — Terrorism Police UK (@TerrorismPolice) June 13, 2017

March 22: 4 killed, 50 hurt in vehicular attack near Parliament

May 22: 22 killed, 116 hurt in Manchester

June 3: At least 6 killed, 20 hurt https://t.co/Vvw8Xxv52j — Oren Kessler (@OrenKessler) June 4, 2017

2017 Has Seen a Terror Attack Attempted in Europe Every 9 Dayshttps://t.co/pkGilxUGM1 pic.twitter.com/7vyBikhFmf — Simon Harding (@gridnash) May 25, 2017

Notwithstanding that arrests have been taking place at a blistering speed: