The completion of the first phase of restoration works at a historic grotto was marked by a royal visit.
The Duke of Gloucester attended the 18th century Wanstead Grotto to see repairs to the landing stage, which are part of a wider restoration programme.
The project was "urgently needed" to stabilise the structure, according to Heritage of London Trust.
The charity funded the work along with City of London Corporation, which manages the grotto.
Conservation work was inspected by the duke, who is ranger of Epping Forest and Heritage of London Trust patron.
He saw the rebuilt retaining wall, with the work also removing "invasive" plant life, the charity said.
The duke also spoke to refugees from its Proud Places programme, which supports young people from challenging backgrounds to get involved with the capital's heritage.
The charity's director Dr Nicola Stacey said: “It has been wonderful to show the duke progress on the grotto.
"It’s one of east London’s hidden gems and so important that it is restored for the public and the local community to enjoy again.”
The grotto was destroyed by fire in 1884 and has since sat as a ruin on the edge of Wanstead Park's ornamental lake.
It was built as a venue for theatrical entertainment with many activities taking place on the lake just in front of it, the charity said.
Inside there were rooms decorated with shells and crystals, mirrors and a pebble floor.
The grotto is on Historic England's Heritage at Risk Register, meaning it is considered to be "at risk".
A planning application by City of London Corporation to consolidate and stabilise the Grade II listed building's landing stages was approved by Redbridge Council last year.
Dr Stacey told the Recorder in August that the charity was involved in discussions to subsequently restore the grotto's façade.
During his visit, the duke also met representatives from Friends of Wanstead Parklands.
The group's chair John Sharpe called the grotto "an iconic feature" within the park.
He said: "We were delighted by the duke's visit and greatly appreciate the personal interest he is taking in this project.
"It's very gratifying to see the grotto's importance recognised by a royal visit as work begins to secure its future.
"The intervention by the Heritage of London Trust is proving a catalyst for critical action.”
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