Councillors defied expectations last night by deferring a decision on a technicality that could have brought the Silvertown Tunnel one step closer to reality.

A Hazardous Substances Consent remains on a controversial gas holder in millennium way, and all the while the license exists the Silvertown Tunnel can only be built but not used.

This is because of a restriction included in the Government’s permission for the controversial tunnel, which was granted last month.

Councillors were asked to revoke the license, which would also mean St Mary Magdalene could open as planned in September – the current situation would mean that part of the outdoor playground would be unusable.

Despite no gas being stored in the historic structure since 2013, councillors were concerned that by voting to revoke the consent they were giving developers a favour – as it would make the land easier to develop.

HSC’s are given on sites where dangerous substances are stored, such as gasholders, in order to avoid accidents.

The government is encouraging councils across the country to revoke similar licenses when they are no longer needed, but by revoking it the council could be liable to pay compensation.

Despite SGN writing to the council to say they would not ask for any cash, councillors were concerned about the greater impact of making developments there easier.

Prior approval has already been given to SGN to demolish the structure, which is a favourite for many in the community, and a petition has since been backed by thousands of people.

Councillor Nigel Fletcher said: “There is no financial benefit but this allows them to develop the land. By approving this we are doing the developer a favour in making their land more developable.”

Councillors were concerned that the decision could end with the council shelling out in compensation, and that it would speed up developments on the site.

Officers assured the planning board that it was not SGN’s intention to seek a payout, but there has been no legally binding word between them.

Cllr Fletcher went on: “There is an issue of historic significance. I know this item does not directly deal with that, but there is that significance and the Silvertown significance.

“We have to look at it more potently, we have an assurance that is not legally binding on the compensation issue. I’m concerned that we don’t make a decision that leaves us open to compensation – and I’m concerned we are making developments more likely without any assurances of what they want to do.”

St Mary Magadalene School is set to open in September, but with the hazardous consent in place it would be unable to use the entirety of its outdoor area because of the technicality.

Cllr Sarah Merrill, chairing meeting, said the order has nothing to do with the potential demolition, and that not revoking it would not stop SGN knocking the structure down.

Councillors backed a referral instead of approving revocation – deciding to wait to be told more about the intentions of the site, the implications of the Silvertown Tunnel and any compensation that would need to be paid.

Councillors voted to push back a decision until July, with three voting against and one abstention.