Video report by ITV News Correspondent Sejal Karia
The knives used in the London Bridge attack were bought from Lidl the day after one of the terrorists hosted a barbecue to celebrate the birth of his daughter, an inquest has heard.
On Wednesday, the court also heard that Khuram Butt, 27, Rachid Redouane, 30, and Youssef Zaghba, 22, could have been intending to target London's busy Oxford Street shopping district, but may have switched destinations en route.
Eight people were killed by the three terrorists as they mowed down pedestrians on London Bridge before rampaging through Borough Market and stabbing people on June 3, 2017.
After the attack, police uncovered "viable" petrol bombs in their hire van and fake suicide vests.
Acting Detective Chief Inspector Wayne Jolley told the hearing about the men's preparations in the days before the attack.
He said all three attackers were working together by at least January 14, 2017.
They regularly trained at the Ummah Fitness Centre in Ilford, east London, and went on Sunday swimming trips to nearby Stratford.
On May 14, Redouane was pictured at Butt's barbecue celebrating the birth of his daughter.
The Ernesto 12 inch pink ceramic ceramic knives were bought by Redouane at Lidl in East Ham at 10.15pm the next day.
On May 29, the attackers were seen on CCTV footage meeting at the fitness centre.
The following day, Redouane went back to the same Lidl to buy wine bottles for the makeshift bombs.
The mock suicide vests worn by the attackers were made from four bottles covered in silver tape attached to a brown belt.
DNA analysis suggested Redouane made the fake suicide belts, with help from Zaghba, the court heard.
On the day of the attack, Butt made an online booking to hire a van from Hertz.
He had tried to hire a 7.5-tonne lorry but the branch he asked to collect it from had closed at 11am that day, the court heard.
Shortly before midday, Butt had gone walking with his family in a park.
He later met up with Redouane, who was with his child.
At around 4.30pm all the attackers were outside Butt's block.
Redouane's red Corsa was later seen arriving at the B&Q in Harold Hill, Romford, to collect the van.
The attackers also bought 29 bags of gravel, which were put in the back of the vehicle to add weight.
The men left B&Q in convoy, with Zaghba driving the van accompanied by Butt and Redouane in the Corsa.
Redouane dropped off his child before joining the others at Zaghba's home in Fairfield Road in Ilford.
The attackers stopped off in the van at a Shell garage at 7.54pm, where they bought diesel, drinks and snack bars before heading to Butt's Barking address.
While there, they loaded up black plastic chairs before setting off at 8.55pm towards central London.
A mobile phone later found in the van held directions to Oxford Street, suggesting the London Bridge target was only identified en route, the court heard.
The attackers mounted the kerb and launched their attack on the bridge just before 10.07pm.
Within 10 minutes, they had killed eight people and injured many more before they were shot dead by police marksmen.