Plumped lips may be a modern beauty trend, but before fillers and Instagram filters there was the humble paintbrush.

The restoration of a 400-year-old painting has revealed how an aristocratic beauty had her mouth and hairline re-touched to make her lips fuller, and forehead smaller.

The restored portrait of Diana Cecil goes on show at Kenwood House in Hampstead later this month, but English Heritage conservers discovered that the painting had received a much later touch up by a different artist.

Ham & High: The conservation also revealed, hidden in a curtain, the date of the portrait and the name of the artistThe conservation also revealed, hidden in a curtain, the date of the portrait and the name of the artist (Image: English Heritage)

Born in 1596, Diana was the great-granddaughter of William Cecil, one of Elizabeth I's closest advisors. Renowned as a great beauty, she hailed from a powerful noble family at the Jacobean court, and married first Henry de Vere, 18th Earl of Oxford, who died a year later, then in 1629 Lord Thomas Bruce 1st Earl of Elgin.

The full length painting depicts her in her 30s and had suffered damage from being rolled up. When conservers removed the yellowing layer of varnish they revealed her lips and hair as they were originally painted, and also discovered, hidden in the painting's curtain, the date it was created - 1634 - and the artist's signature; Cornelius Johnson.

English Heritage collections conservator Alice Tate-Harte said: “As a conservator I am often amazed by the vivid and rich colours that reveal themselves as I remove old, yellowing varnish from portraits, but finding out Diana’s features had been changed so much was certainly a surprise!Ham & High: The painting with Diana's lips and hairline restored goes on show at Kenwood House from November 30.The painting with Diana's lips and hairline restored goes on show at Kenwood House from November 30. (Image: English Heritage)

"While the original reason for overpainting could have been to cover damage from the portrait being rolled, the restorer certainly added their own preferences to ‘sweeten’ her face. I hope I’ve done Diana justice by removing those additions and presenting her natural face to the world."

Kenwood is home to two portraits of Diana Cecil; one painted by artist William Larkin when she was around 15, and the work by Cornelius Johnson, which shows her in a fashionable blue satin bodice and full skirt.

By contrast to the earlier portrait, elite fashion is characterised by understated elegance. Plain silk, satin or taffeta were all the rage, with focal points, such as the red ribbons laced across the bodice, a red rose at her breast, and a patterned fan.

The restored portrait of Diana Cecil goes on display at Kenwood House on November 30 alongside a painting of her husband Thomas Bruce 1st Earl of Elgin.