The failure to install barriers on London Bridge in the aftermath of the Westminster Bridge terror attack in the UK capital was “unreasonable”, an inquest has heard.

Gareth Patterson QC, representing six of the eight victims’ families said it had been a mistake not to take such preventative action to avoid a recurrence of the attack on the Palace of Westminster on 22 March 2017.

On 3 June, the same year, three attackers – Khuram Butt 27, Rachid Redouane, 30, and Youssef Zaghba, 22 – using a similar modus operandi, mowed down pedestrians on London Bridge before stabbing people in and around the Borough Market area.

The inquest at the Old Bailey in London heard that, exactly a month before the London Bridge attack, Sergeant Matthew Hone, in an email to City of London police colleagues, wrote that the location was probably his “biggest concern” in terms of an attack of low sophistication. The bridge had already been identified by the force as being in the top five of likely sites for an attack in the City of London.

But Jane Gyford, who was the City of London police commander of operations and security at the time, said the location did not meet the criteria for installing barriers, namely a specific threat or large public event.

Gyford told the inquest: “There was no intelligence picture to suggest London Bridge was going to be the site of an attack and therefore we were looking at the picture as a whole and we were taking action.”

She was challenged by Patterson, who said barriers would have been a prevention against attack in the way that unpredictable, highly visible deployments and armed vehicle response units, could not be.

He said: “This particular place was crying out for protection was it not? My suggestion is that, whether [the decision-making process] was rigorous or not, the wrong decision was clearly made, and the unreasonable decision was made, not to install barriers.” Gyford replied: “I disagree.”

On Wednesday the inquest had heard from Lucy D’Orsi, deputy assistant commissioner specialist operations at the Metropolitan police. She said that the Westminster assault had been considered a strike on parliament rather than a bridge attack. “The view was that the bridge was a road used by the terrorist [Khalid] Masood to carry out his attack on parliament,” she said.

Those killed by the London Bridge attackers were Christine Archibald, 30; Sébastien Bélanger, 36; Kirsty Boden, 28; Ignacio Echeverría Miralles De Imperial, 39; James McMullan, 32; Alexandre Pigeard, 26; Xavier Thomas, 45; and Sara Zelenak, 21. Another 48 people were injured, 19 of them critically.

The inquest continues.