Concert promoters AEG Presents have apologised "for the inconvenience caused" at last weekend's Michael Bublé show in Hatfield Park.
The chart-topping Canadian singer played a huge outdoor concert in the grounds of Hatfield House on Saturday, July 23.
Traffic-related incidents were reported both before and after the event.
Ticket holders were stuck for hours in queues getting into the Hertfordshire park before the concert and some missed the start of Bublé's set.
There were further problems at the end of the evening, with concert-goers taking hours to get out of the venue's car park amid chaotic scenes.
The day after the concert, Hatfield Park released a statement saying: "Last night some attendees experienced significant disruption during their arrival at and departure from AEG presents an Evening with Michael Bublé at Hatfield Park.
"We are working with AEG to understand what went wrong."
The statement added: "For some, this event has been memorable for the wrong reasons. We regret that fact deeply and will now review the event’s shortcomings with the organiser."
AEG Presents have now issued a statement, shared on Hatfield House's website and social media channels yesterday (Friday).
AEG's message said: "Unfortunately, following an enjoyable evening in concert with Michael Bublé at Hatfield Park, a portion of attendees experienced delays and issues with exiting the venue’s car park.
"While a comprehensive traffic management ingress and egress plan was agreed ahead of the event, a large number of contracted traffic management staff left after the ingress following the arrival of concert-goers, resulting in issues carrying out the egress plan.
"As such, some guests experienced excessive delays and disruption."
The statement continued: "Upon learning of the issue, Hatfield Park and other event staff offered their immediate assistance for which we are extremely grateful.
"Unfortunately by the time this was implemented the situation was already irretrievable and customers were stuck trying to exit.
"This was a less than ideal experience for fans and we apologise profusely for the inconvenience caused on what was an amazing night of music.
"You can contact AEG Presents with customer feedback directly using the below form: https://aegpresents.zendesk.com/hc/en-us/requests/new"
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