Sipping a cappuccino in the elegant surroundings of London's former County Hall, Joanna Lumley appears to have it all: fame, fortune and a career that frequently takes her to exotic locations.
But she admits to having one ambition unfulfilled.
'If I started my life again I would very much love to be a carpenter or an engineer - someone who can build things,' she says.
She confesses to having 'the most enormous interest in architecture and engineering of every kind'.
'I couldn't be more fascinated by it all. I drive around madly on my Sundays in the city to see the new buildings that are being built - the good ones, the bad ones and the ones I think pay respect to the surrounding area. I have been drawing dream bridges since my early 20s,' she adds.
Lumley's latest non-acting project - she has famously trekked in the Karakoram mountains and been stranded on a desert island for a survival documentary - may see her fulfilling at least part of her ambition. She has conceived the idea for, and is energetically promoting, a £19M bridge across the Thames in memory of Princess Diana.
Although she met the princess only once in the line-up for a film premier, Lumley believes the Government's plans to build a memorial fountain in a royal park would not do her justice.
'It would be a pity for somebody who was so vital and so hugely known to have a memorial that was like a sombre tomb rather than something that was alive and carried her name. A bridge is symbolically one of the most powerful structures that man can make,' she says.
The bridge would not, however, be purely symbolic - Lumley has thought long and hard about its location. Her solution would open up a much-needed pedestrian route between St James's Park and Jubilee Gardens, close to the site of the Millennium Wheel on the south bank of the Thames. If built, the bridge is intended to cross the river just to the east of Big Ben.
'I have sat like a stalker day and night to try and work out the impact of the bridge on the traffic. Very few things would be put out by the position I have chosen,' she says.
Lumley's concept is to construct a light and graceful steel structure clad in semi-opaque glass lit from within. It would be planted with trees, closed to vehicular traffic and up to 20m wide in places, providing an area of 'relaxation and contemplation' in the middle of the river.
With help from Ove Arup & Partners principal maritime engineer Greg Haigh, Lumley has already sounded out the Port of London Authority, the body which governs navigation on the Thames, on the possibility of building the bridge.
After initial scepticism, the PLA eventually set down some preliminary ground rules.
'Because of the shape of the river bend at this point, the rush of the tide and the scour of the bed, the PLA has said that we are only allowed two piers in the river,' says Lumley.
This would present an interesting technical challenge if the concept of a slender design is to be maintained. The central span of the bridge would be 160m long - 16m longer than that of the much narrower Arup-designed Millennium Footbridge under construction a kilometre to the east (NCE 29 April). And Lumley is adamant that it should not be a cable-stayed or suspension bridge in the traditional sense.
'What you really don't want is something overhead. The point of it is that you can stand and see the sky and the whole of the river uninterrupted,' she says.
Lumley hopes to get a design competition going in the next three months. Funding would be raised by public subscription and corporate sponsorship and would be 'no problem' she claims.
The main stumbling block is getting planning permission. Lumley has already met Westminster and Lambeth council officials but believes the decision will rest with whoever is elected Mayor on May 1 next year.
'On May 2, I will be hammering on the Mayor's door,' she says.
Despite the potential difficulties, Lumley's enthusiasm is undimmed. 'This will be thrillingly exciting at every level,' she says.
'I would love the construction and engineering industry to feel this is a viable and attractive proposition which, in the long term, would make sense to the integral structure of London.'
She adds: 'If the bridge goes ahead I will be there from the first day of drilling. I would have to get a permanent pod on the Millennium Wheel so I can watch the whole process.'