While more than three quarters of the arrests were related to worldwide terrorism, there was a sharp rise in the number of arrests for domestic terrorism (from 10 to 52).
"Significantly, it's the highest number of arrests in a year since they began recording terror arrest statistics back in 2001 after the attacks on the Twin Towers and the Pentagon in the US".
British police made a record 379 arrests for terrorism-related offences a year ago, official figures show.
The figures have soared by 68 per cent since previous year, reaching the highest level since records began.
Another man died following a van attack outside a mosque in Finsbury Park, London on June 19, 2017.
The United Kingdom has suffered a series of terror attacks this year.
GETTYThe UK has been hit by a series of attacks this year
Security Minister Ben Wallace said the figures show police and security services responding to "an unprecedented period of terrorist activity in the U.K".
The new figures show a 60% jump in arrests linked to worldwide terrorism, from 184 to 294.
"That's why we're looking at such a high number, but they are still pretty significant".
By the end of June this year, 204 people in the United Kingdom were in custody for terrorism-related offences in the country.
Domestic terrorism refers to activity where there are no links to either Northern Ireland-related or worldwide terrorism.
Of the 379 arrests in the 12 months to the middle of this year, 123 resulted in a charge, including 105 where suspects were charged with terror-related offences. A further 189 people were released without charge, and the remainder were either on bail, or police investigations and other actions were ongoing.More news: Investors Heaps up on Sirius XM Holdings Inc. (SIRI)