Police officers were called to control crowds at the opening of a new department store in Oxford Street.
Around 50 Primark stores have been opened in England this year.
Reinforcements had to be brought in to control the crush when pressure from hundreds of people queuing at the new Primark store broke one of the doors.
Less than two hours after doors opened, shoppers were being let into on a one in, one out basis.
The 70,000 sq ft (6,500 sq m) store near Marble Arch sells clothes for men, women and children and homeware.
Centre of gravity
Geoff Lancaster from Primark said: "We've been dealing with the police throughout the run-up to this and we had double security drafted in for the opening.
"But there have been openings all round the country, we've done 50 stores in England this year so we're quite used to opening. But this is unprecedented."
Jeremy Baker, retail analyst from London Met University said the store would have a big impact.
He said: "Primark is such a big name and made such a difference to British shopping that it's just going to pull the centre of gravity from the other end of Oxford Street, right up to here."