The Home Office has announced that there were 379 arrests in Britain in the 12 months to June.
Home office stats have shown there were a record 379 arrests for terrorism-related offences in the country in the year ending in June 2017.
The number of terrorists in British prisons has also risen over the past year - by 35 per cent to 204.
The United Kingdom has suffered a series of terror attacks this year. He explained: "That's why we're looking at such a high number, but they are still pretty significant".
The figures show that of those who have been arrested, 32% result in a charge.
Around half (189) of those held were released without charge, while others were released on bail (54) or faced "alternative action" (11).
Deputy Assistant Commissioner Neil Basu, the senior national co-ordinator for counter-terrorism policing, said: 'We're taking every possible opportunity to disrupt terrorist activity be it making arrests for terrorism offences, intervening where there are signs of radicalisation, or working with communities to prevent terrorists operating in their area'.
The 420% increase in terrorism with no worldwide or Northern Island related links comes amid mounting concern over far-right extremism.
The police and MI5 are typically running about 500 investigations involving 3,000 individuals at any time, and at least 20,000 former "subjects of interest" are also kept under review, according to the Sky News website.
Since mid-2013, the authorities have thwarted 19 plots - including six since the Westminster attack.
The current United Kingdom threat level for global terrorism is severe, which means an attack is highly likely.