The National Army Museum has quietly removed from display a 19th-century looted braid of hair which the Ethiopian government has requested back as a national treasure.

It came from the head of the Emperor Tewodros II, who killed himself at the end of the British invasion of Ethiopia in 1868 rather than being taken prisoner. He shot himself with a pistol that had been a gift from Queen Victoria.

His clothes were torn from him and the braid was cut off and taken to the UK, along with hundreds of objects pillaged by an expeditionary force under the command of Lt Gen Sir Robert Napier.

It was a military expedition to save British hostages, including the British consul, Charles Cameron, who had been kept in chains for more than two years.

The army destroyed the emperor’s Maqdala mountain fortress in northern Ethiopia. It brought back treasures, transported on 15 elephants and 200 mules, that were eventually deposited in various British institutions.

For years, the braid has been held at the National Army Museum in Chelsea. It was removed from view following a visit in April by the Ethiopian ambassador, who made an official call for its return. Ethiopia wants the braid to be interred with the rest of the emperor’s remains at his final resting place at the monastery of the Holy Trinity at Quara.

Sources said the museum discussed the request at its May council meeting and that the director was asked to write a report recommending possible outcomes, which were to be communicated to the Ethiopian embassy before 1 September.

The museum declined to comment on Monday. The Ethiopian embassy in London confirmed that a restitution request has been made.

Ethiopia has long called for Britain to return the looted artefacts. In April, the Victoria and Albert Museum announced that a gold crown was among treasures that could be returned on long-term loan.

Its director, Tristram Hunt, noted that even in the 19th century this episode of British and Ethiopian history “was regarded as a shameful one”. He acknowledged the “objects’ difficult past and their rich Ethiopian cultural heritage”.

The Ethiopian government is calling on the British Museum and other UK custodians of treasures seized at Maqdala to follow the V&A’s example. Part of the problem is that institutions like the British Museum do not have legal powers to deaccession.

In 2010, Westminster Abbey was criticised by campaigners over its refusal to return a looted tabot to the Ethiopian Orthodox church. Tabots – small tablets that symbolise the Ark of the Covenant – are regarded by 35 million Ethiopian Christians as so sacred that only priests are allowed to look at them. The abbey has a stone tabot inlaid at the back of an 1870s altar in the Henry VII Lady Chapel, where it is visible to anyone peering around its left side.