Under the hammer: Princess Michael's china cats and Guns 'n' Roses memorabilia

To a casual observer, it looks like the sort of bric-a-brac that Derek Trotter might flog from the back of his Robin Reliant.

The hundreds of gifts and trinkets being auctioned on Friday for as little as £5 range from reproduction furniture and table lamps to tennis rackets, pottery cats, and an old video recorder.

But this will be no ordinary house-clearance, for the cut-price items due to go under the hammer were once the contents of Nether Lypiatt Manor, Prince and Princess Michael of Kent's former country home.

The Kents, first cousins to the Queen, sold the eight-bedroom Gloucestershire manor and its contents for £5.75m to the Labour peer Lord Drayson in April. They now live at a grace-and-favour apartment in Kensington Palace and, like other couples who decide to "downsize", have been forced to sort through 25 years' worth of clutter.

On Friday morning, about a hundred lots of "residual items" will be sold to the highest bidder at the saleroom of Moore, Allen & Innocent in Cirencester.

Buyers will have the chance to acquire anything from the Princess's Orbitrek exercise machine (estimate: £5 to £10) to her son Lord Frederick Windsor's childhood table football set (£20 to £40) and pop posters from his bedroom.

An acoustic guitar "housed in a faux crocodile velvet-lined case" will go for an estimated £40 to £60, while an unwanted portrait of Prince Michael by the artist Evan Fotis is expected to fetch between £20 and £40.

Chris Surfleet, the firm's senior auctioneer, said none of the lots was expected to raise more than £150. The Kents have decided to save more valuable items for two specialist auctions in September and October.

"We're not expecting to sell this level of items for much, but we will have to find out," he said. "With the specialist items we are expecting bidders to dig a little deeper. There's lots of history to these items so that won't do their chances any harm.

"A lot of curious people will come to look at the contents of a royal home. Some lots might sell at a premium because of the royal provenance, and other buyers might try to re-sell their purchases on eBay, but that's what public auctions are all about."

Most items included in the auction are unwanted furniture and ornaments. A "Herend porcelain figure of a squirrel eating a nut" is expected to go for between £40 and £60, while two sets of four dining-room chairs are valued at just £10.

However, some may also excite buyers interested in royal memorabilia. A certificate presented to Prince Michael by the RAC in 1992 following a Bentley rally is estimated to fetch between £20 and £40.

A spokesman for the Prince and Princess said that the proceeds of Friday's sale are to be donated to charity. It isn't clear if the same will apply to more expensive items that will be sold at later auctions.

Princess Michael was forced yesterday to withdraw from the sale a present from her friend Paul Johnson, the historian. A spokesman said the gift - a painting of the garden of Cockermouth Castle inscribed with the message "to my favourite Princess" - had ended up in the catalogue "by mistake".

The auctioneers, who earn a commission of 15 per cent from each item sold, said the Kents were unlikely to attend the sale.

The sale marks the second royal "house clearance" of recent months. In June, Viscount Linley raised £13.5m when his mother Princess Margaret's possessions were sold at Christie's.

The late Princess's trademark cigarette case fetched £102,000, while an anonymous bidder paid £680,000 for a portrait of her by Pietro Annigoni, dating from 1957.