Deputy Assistant Commissioner Dean Haydon urged the public to remain watchful as the UK threat level remains at severe, meaning an attack is highly likely.
Mr Haydon, the senior national coordinator for counter-terror policing, told Sky News: “I’d encourage all members of the public to remain vigilant.
“The police and security services are working extremely hard, foiling and disrupting terrorist attacks all the time.
“It (the terror threat level) has gone to critical on two occasions, on the back of the Manchester and Parsons Green attacks, but we’re currently at severe, which means an attack is highly likely.”
British spies have disrupted terror plots at a rate of roughly one per month over the past year, MI5 head Andrew Parker said recently.
Mr Haydon’s comments come as survivors of the London Bridge atrocity are to be joined by bereaved families, emergency service staff and politicians for a remembrance service at Southwark Cathedral on Sunday.
In tribute, candles will be lit by victims’ relatives before an olive tree, called the Tree of Healing, is planted in the cathedral grounds using compost from flowers left on the bridge after the murders.
Elsewhere Margaret Gilmore, a senior national security analyst, told Sky News although Islamic State was suffering in Syria and Iraq, it still poses a threat in persuading fanatics to carry out attacks in the West.
The attacks on the bridge and Borough Market killed eight and wounded almost 50 people on June 3 last year.