More than £40,000 in cash donations to a cancer charity was stolen from a safe following a fundraising festival.
Thousands of people attended the annual Summer Soulstice Festival in Barnet's Old Elizabethans Memorial Playing Fields on June 23 which collected money for Cherry Lodge Cancer Care charity.
£45,000 pounds in cash raised at the festival was stolen from a safe in the pavilion building in Mays Lane.
Police were called to the burglary at 7am on June 25.
Police Detective Inspector Julian Worrell, who is leading the investigation, said: "A large sum of money had been generously donated by members of the public to help support a local cancer charity.
"We all have family and friends that have been affected by this terrible illness and some person or people have selfishly stolen this charitable money for their own gain.
"I am appealing to anyone that can provide any information to help assist us in finding those responsible for this crime and hopefully recover the cash.
"The burglary happened in a remote area around Mays Lane - did you see anyone acting suspiciously? Or are you aware of anyone unexpectedly in receipt of a large sum of cash?"
He added: "Any information may be of vital use and I would urge you to contact Barnet CID as soon as possible."
Members of the Summer Soulstice Festival committee says they "feel crushed" from the theft that has "put all [their] future fundraising events at risk."
A statement on a fundraising page set up by the festival committee to recoup the stolen sum read: "We fear that this money, which everyone generously helped to raise that day, will never be seen again.
"The long-term effects of this theft on our charity event has created uncertainty and has seriously undermined the chances helping people in the local community. Even more worrying is that this has also put all our future fundraising events at risk.
"All of us on the Summer Soulstice committee and in our event crew, are feeling crushed from this awful incident, but we want this annual event, which brings both friends, family and communities together, to have longevity and continue fundraising."
The crowdfunding page has so far raised more than £26,000.
You can donate to the Summer Soulstice's JustGiving page here.
No arrests have been made in connection with the burglary which Brent police is investigating.
Anyone with information is asked to contact Barnet CID on 020 8733 4125 or 101 quoting Crime Reference 1481/25June.
Alternatively if you wish to give information anonymously contact Crimestoppers on 0800 555 111 or online at www.crimestoppers-uk.org