An ageing aristocrat is in need of some tender loving care.

But Sir Richard Fanshawe’s portrait, hanging in Dagenham’s Valence House, could do without a breath of fresh air to ensure it survives the next 500 years.

Changes in temperature, humidity and rooms full of admirers breathing on the exposed canvas threaten to cause cracking to its delicate surface.

To save it for future generations it needs a modern frame and glazing – which could cost up to £1,000.

Staff at the Becontree Avenue museum are currently fundraising to pay for a special ultraviolet glass covering to stop fading and create a protective microclimate inside the picture, protecting it from changing room conditions.

Though glazing is controversial, curator Leeanne Westwood says it is vital for the portrait’s survival.

“This painting is irreplaceable,” the 36-year-old explained. “It’s one of the largest in the museum’s collection.”

The proposed conservation follows an incident earlier this year when an admirer of another canvas accidently scratched it after running a hand across its exposed surface.

Leeanne believes the portrait is so special because it can be interpreted in many ways.

“The painting is full of symbolism, with a greyhound in the foreground symbolising Sir Richard’s loyalty to the crown,” she said. “In the shadows there’s also a mask which symbolises Sir Richard’s love of the arts.”

The portrait was painted in 1644 by William Dobson who is regarded by experts as the best British-born portrait painter of the period.

Leeanne added: “People who see it are always very, very impressed.”

The delicacy of the painting means that it has been on display just three times this year – but it could soon become more durable.

Volunteers are leading a fundraising day on Saturday which includes talks, a table top sale and a secret codes trail.

Admission is free, with the event taking place from 10am to 3.30pm.