Nature lovers are up in arms that recreation land on Leyton Marsh was not returned to the community on Monday - the date repeatedly promised by Olympic chiefs since the land was used to build a basketball training hall.

The Lea Valley Regional Park Authority (LVRPA) loaned the Olympic Delivery Authority (ODA) the green space behind Lea Bridge Road to build the 12m high temporary structure for the 2012 Games.

Many Hackney residents opposed the plans on the basis that the Metropolitan Open Land had protected status - but in January Waltham Forest Council’s planning committee gave the green light to development, citing exceptional circumstances.

Opponents had wanted to see a beneficial legacy for the community from any facility built, rather than a temporary hall on a much-used green space next to a site of special scientific interest (SSSI).

Some people felt so strongly they set up camp next to the site, and blocked lorries from entering the building site until the ODA obtained a costly injunction against any protest at the High Court in March.

Caroline Day from the Save Leyton Marsh (SLM) group, which formed to oppose the application, said: “When objecting to destruction of the land for the temporary venue, SLM were continually re-buffed with the claim that the venue was only “temporary” and that the land would be “restored to its original condition” by October 15.

“The ODA and LVRPA used these claims in order to try and present any protest against their plans as ill-founded and unreasonable.

“However protesters were vindicated in their concerns by multiple breaches of the conditions of the original planning permission, which involved laying concrete foundations and excavating far deeper than the 15cm that was originally claimed,” she added.

An unexploded bomb was uncovered in the process, along with tonnes of material contaminated with asbestos – which is dangerous to human health when airborne – which was then left uncovered in piles on the site for weeks.

The topsoil is too compacted and water-logged for the turf to be laid, and the ODA has blamed the weather for the delay in reinstating the land which will be at least two weeks.

An ODA spokesman apologised for any inconvenience caused.

“We have received expert advice in light of the recent heavy rainfall advising against completing laying the turf until conditions on the ground improve,” he said.

“We would like to reassure residents and stakeholders that restoring the land at Porter’s Field in accordance with our reinstatement plan remains an urgent priority for the ODA.”

A celebration for the return of the land had been planned for Sunday October 21, but the gathering still went ahead anyway.