How is a major concert organised at short notice?

The concert, which features Justin Bieber and Grande, will be broadcast on BBC One

A benefit concert in aid of the victims of the Manchester bombing is being organised for Sunday, but how much work goes into planning an event in so little time?

"To be honest, it's possibly the hardest task I've ever had to undertake," says Melvin Benn in an interview with the BBC about the One Love Manchester concert he is co-producing.

Benn, boss of Live Nation subsidiary Festival Republic, is the man behind some of the UK's biggest music festivals, including Latitude, Reading and Leeds, Wireless and Download.

"We started the conversations on Friday evening, here we are on Wednesday and the concert is on Sunday. It's eight-and-a-half days to put it together. It's an incredible amount of work," he says.

• Stars to join Grande for Manchester gig

• Talent final moved to avoid Grande clash

• Fans' concerns over Ariana Grande tickets

• Everything you need to know about the concert

One Love takes place at the Emirates Old Trafford in Manchester on Sunday, and will feature in its line-up Justin Bieber, Coldplay, Katy Perry, Miley Cyrus, Pharrell Williams, Usher, Take That and Niall Horan.

Ariana Grande will also perform for the first time since last Monday, when 22 people were killed and 116 injured in a suicide bombing after a concert she played a concert at Manchester Arena.

Coldplay will also perform at the concert this Sunday

Free tickets are being offered to those who attended the original gig, with proceeds from sales to the general public raising money for Red Cross's Manchester Emergency Fund.

"Clearly there are some families suffering bereavement or who have family members in hospital, and we're trying to do as much as we can to look after them as a priority, as well as all the rest of the fans that came," Benn says.

"We felt offering free tickets to everybody that was there on that night was the minimum we could do. The rest of the people that are coming will be the people who will be providing the money for the fundraising, but for those fans that were there we felt this was a good way of honouring those that lost their lives."

The gig will naturally require a great deal of logistical organisation, but Benn says "everybody is pulling together".

Miley Cyrus will join Katy Perry and The Black Eyed Peas at Sunday's concert

"Greater Manchester Police, Trafford Borough Council, Manchester City Council, Transport for Greater Manchester, all pulling in the same direction to make this work, as well as the music industry and all the pop stars, it's incredible really," he says.

"The way Manchester has responded [to the attack] has been phenomenal, and I think that's been part of the inspiration for Ariana, to want to come back so quickly."

Benn added that Grande was "traumatised, absolutely traumatised immediately after the gig, in complete shock, but she knew she had to do something".