The much-delayed memorial to Britain’s worst wartime civilian disaster has been stalled at the last hurdle by the installation firm going into liquidation and delayed planning negotiations to get it finished.

The partly-completed ‘Stairway To Heaven’ memorial in London’s East End a few yards from the air-raid shelter tragedy won’t be ready in time for this Sunday’s 74th anniversary service to remember the 173 men, women and children crushed to death on March 3, 1943.

The memorial in Bethnal Green Gardens should be completed by the summer after 10 years campaigning, when the inverted wooden staircase now having its finishing touches in the factory is lowered by crane onto the concrete support and plinth.

“The legal agreement we needed to add that final part took eight months to negotiate,” the trust’s Sandra Scotting told the East London Advertiser.

“There was no point building the ‘stairway’ bit on top as we would have had to pay for it to be stored.

“The company that was to install the ‘stairway’ went into administration in December, which was another blow to our timetable.”

The trust charity finally received agreement from Tower Hamlets council for the last stage to go ahead — but is now having to find another company to finish the project.

The surnames of those killed trying to get to safety in the underground shelter are being read during Sunday’s service starting at 2pm at St John on Bethnal Green Church while 173 candles are lit, one for each soul lost.

This is followed by a church-led procession with Pearly kings and queens, TV’s Groundforce presenter Tommy Walsh, Bethnal Green’s MP Rushanara Ali and Tower Hamlets’ Mayor John Biggs.

The last few survivors from 1943, many now in their 80s and 90s, and relatives of those who died, lay wreaths by the memorial plinth, 74 years on from that fateful night.

A crowd trying to get to safety surged onto the narrow, unlit stairway toppling onto a woman carrying a child who had tripped. They, too, were crushed as more people poured in behind them.

But their deaths were for nothing. The air raid alert turned out to be a false alarm, possibly caused by anti-aircraft rocket guns being fired in Victoria Park when a lone aircraft was spotted.

There was no German air-raid that night.