Parts from Boris Johnson’s useless water-cannon trucks could be salvaged from the scrapheap and placed in an exhibition, under plans being considered by the Museum of London.

The museum’s director, Sharon Ament, revealed to the Guardian that she had tried to buy one of the three vehicles outright after they were first put up for sale two years ago.

At the time, she was told they could not be sold to a museum for legal reasons. The previous owners, the German police, had stipulated that they could only be sold on to a European policing or civil protection organisation.

After Johnson bought the vehicles they were banned for use in the UK by Theresa May when she was home secretary. And no other European authority wanted to buy them.

But now that three trucks have been sold to a reclamation yard at a net loss of more than £300,000 to the taxpayer, the museum is looking into purchasing selected parts of the vehicles for its collection.

A spokesperson said: “Many of our most interesting objects come from scrapheaps. Indeed, almost all archaeological finds are human waste of some sort. Whether it’s possible to salvage a part of the water cannon from the scrapyard, I don’t know. But even a section of it could help to tell a complex story about policing in the capital.”

Reclamations Ollerton, a scrap-metal yard in Nottinghamshire, confirmed work had already begun on breaking up the vehicles, which it purchased for £3,675 each. One of the yard’s staff, who would only give his name as John, said the water guns had already been removed from the vehicles before they were sold.

Ament had been hoping to acquire one of the vehicles as a way of drawing visitors to the museum’s planned new site in part of the former meat market at Smithfield, central London.

She said: “The museum made an informal enquiry when the sale was first discussed. However, with great regret, there were legal reasons why the water cannon could not be sold. The water cannon says something interesting about how we police, or have chosen not to police, London.”

The museum’s spokesperson added: “Were it to be available to us, a water cannon purchased by a former London mayor could have been a significant object within our collection and allow us to tell a complex story about modern policing in the city. Our future home at West Smithfield has much much more space to display objects than our current building at London Wall.”

He went on: “Our curators keep their ears to the ground to make sure that at the very least we’re considering significant objects that tell important stories about contemporary London.”

The museum is developing a reputation for exhibiting artefacts associated with stories in the news. Earlier this year it acquired part of 250m fatberg extracted from London’s sewers for a temporary exhibition.