LONDON (AFP) - The ashes of late British prime minister Margaret Thatcher were laid to rest alongside the remains of her late husband Denis in London on Saturday, at a military nursing home she had long supported.

An oak casket containing the ashes of Britain's first and only female prime minister, who died in April after suffering a stroke at the age of 87, was placed in the leafy grounds of the Royal Hospital Chelsea nursing home beside those of Denis, who died in 2003.

A plaque bearing the simple inscription "Margaret Thatcher 1925 - 2013" was being erected at her final resting place.

Thatcher's twin children Mark and Carol were among the small group of mourners who gathered for a private service at the nursing home's chapel, along with Mr Tim Bell, who masterminded her three successful general election campaigns, and Ms Cynthia Crawford, her loyal personal assistant for more than three decades.

In power between 1979 and 1990, the former Conservative leader was Britain's longest-serving prime minister of the 20th century.

A dozen Chelsea Pensioners - army veterans who live at the historic retirement home in central London - formed a guard of honour, dressed in their distinctive scarlet coats.

Thatcher was a long-standing supporter of the Royal Hospital Chelsea, which in 2009 opened a state-of-the-art care home named in her honour, the Margaret Thatcher Infirmary.

The hospital was founded in 1682 to provide former soldiers with a suitable place to spend their retirement.

Thatcher was cremated after her ceremonial funeral on April 17, which was attended by leaders from around the world.

Her death sparked heated debate over her legacy, with supporters arguing that her radical free-market reforms saved Britain from economic decline, but critics saying they left millions of people jobless and created a culture of greed.