David & The Queen's project

The Queen may be our longest-serving monarch, but even she admits she is unlikely to be around very much longer.

She acknowledges her mortality in a joke with Sir David Attenborough in a conservation documentary due to air next year.

The pair, both 91, are chatting in the grounds of Buckingham Palace when he says that because of climate change 'there will be all kinds of different trees growing here in another 50 years' time'.

Photo / PA

The Queen replies: 'I won't be here though' – causing Sir David to burst out laughing.

She then points out a bent sapling and asks someone off camera: 'Is it meant to be like that? Somebody sat on it I think at a garden party.'

The first image from the documentary was released today and shows the Queen and Sir David talking beneath a large boom mic. 

The monarch is dressed in a feminine floral dress without a coat, suggesting the filming took place earlier this year. 

She appears perfectly at ease with Sir David and is seen chuckling as he stands beside her. 

At one point in the programme the pair were drawn to a chestnut tree bursting with conkers. 

As they turned away the Queen turned to him and asked: 'Was it recently that someone tried to stop children playing conkers?'

Due to be shown next year, the ITN documentary will follow the progress of the Queen's Commonwealth Canopy project. 

The Queen's Commonwealth Canopy project initiative aims to preserve areas of indigenous forest across the 52 countries of the Commonwealth, representing the lasting legacy of the Queen's leadership.

-Daily Mail.