Three people were trapped in the external glass lift at Portsmouth's Spinnaker Tower today – its opening day – but the tower's operator, Heritage Projects, has denied that it detracted from what it says was a very successful launch.

The incident was a further embarrasment to the 170m (574ft) tower project, which finally opened to the public in Portsmouth Harbour today, after being delayed since mid-2004.

The people trapped in the lift were all connected to the Spinnaker project and were testing the lift when it stopped.

The group included Portsmouth City Council's project manager, David Greenhalgh.

Engineers were forced to abseil down the tower in an effort to release the group, who were trapped inside the panoramic lift for around an hour.

Despite the lift problems, the opening of the tower was hailed as a success by Juliana Delaney, managing director of Heritage Projects – part of Continuum Group.

"We were expecting around 500 people to visit the tower during the first day," she said.

"But after just three hours, we had received 1,000 visitors – the first people were queuing up at 6am for the 10am opening."

The attraction – which is taller than the London Eye, Blackpool Tower and Big Ben – features three glass encapsulated viewing decks positioned at 105m, 110m and 115m.

View deck I is fitted with a glass floor, reported to be the largest in Europe, while view deck II has two multimedia stations showing the history of the harbour.

The top deck – The Crow’s Nest – is open to the elements.

When operational, the panoramic glass lift will take visitors up and down the outside of the tower – for an additional cost. Most guests however will use the high-speed internal lift.

The tower offers views of the harbour and out towards the Isle of Wight, across a distance of up to 23 miles.

The £38m Spinnaker Tower is the centrepiece of the Portsmouth redevelopment project and received funding from the Millennium Commission.

However, despite being a Millennium project due to be completed on 31 December 1999, work did not get underway at the tower until September 2001.

The original completion date was moved three times after one construction company pulled out and a consortium was dropped. Details: www.heritage-projects.co.uk or www.spinnakertower.co.uk