Charities have attacked the London Marathon over its entry system, branding the event a “closed shop” that allows the same organisations to benefit every year.

They said the model used to allocate places is “unfair” as it leaves the vast majority permanently squeezed out of the lucrative fundraising opportunities on offer.

But the marathon is finally bowing to pressure after two decades of complaints, admitting that it is reviewing the system to allow a broader range of charities to take part.

The vast majority of charity places are tied up in a “golden bond” system established in 1993. Each bond provides five places in the marathon for five years. Once a charity has a gold bond it can renew it in perpetuity.

For those 700 organisations quick and savvy enough to snap them up - and some charities have hundreds - the event is a crucial lifeline.

But for the rest, just getting one place in the marathon is considered “gold dust”.