A word of warning to anyone tempted by the “investment potential” of souvenirs of Prince Harry and Meghan Markle’s forthcoming big day. History suggests there isn’t any.

“The market makes a big distinction between items that are mass produced and those that are very personally linked to the personalities involved,” says Noelle McElhatton, editor of the Antiques Trade Gazette.

We Built This City’s wedding T-shirt. Photograph: We Built This City

Believe it or not, this includes stale wedding cake. “It’s very common for royal couples to commission a very big cake and for this to be parcelled up and put into commemorative tins,” McElhatton says. “What sells really well, because there’s a premium for anything associated with Diana, is wedding cake from her 1981 marriage to Charles.” One slice of this is up for auction in Las Vegas next month and is expected to fetch £800.

In other words, you can have your cake, but don’t eat it (unless it is from the 1986 wedding of Prince Andrew and Sarah Ferguson, in which case, tuck in – no one’s interested).

It’s best, therefore, to think of 19 May not as your great-grandchildren’s golden ticket to Antiques Roadshow 2101, but as a chance to celebrate the latest episode in our gaudy royal soap opera with a bit of gilded tat of your own. It is gilt by association.

Wedding mug from We Built This City. Photograph: We Built This City

At the posh end of the scale, £25 gets you an official mug from the Royal Collection, its decorative borders “inspired”, apparently, “by the mid-13-century Gilebertus doors at St George’s Chapel”. As a further mark of its ethereal exclusivity, it is “not suitable for use in a dishwasher or microwave”.

The gifts on offer at We Built This City are far less formal, which somehow suits this royal couple. If you buy your tea towel (£25), mug (£20) or T-shirt (£40) from the For Richer for Poorer range, all profits will go to help the homeless people of Windsor, whose unwanted right to shiver on the streets was at one point in jeopardy. More crafty still is the range of goods on offer at etsy.com, where delights from dubious dolls to jewellery and mugs – lots of mugs – await.

All of which may leave you hankering for the relative simplicity of the £3.99 melamine snack tray from eBay. At least that’s under no illusions about itself.