Perhaps you know that things are healing when, after centuries of violent tyranny and pillage, the British empire comes down to arguing over postboxes. In Hong Kong, where 59 of the old colonial postboxes remain, the postal service has announced that it plans to cover the royal insignias with a metal plaque – in order to avoid “confusion”. (The boxes have already been painted green and had the Hong Kong Post’s logo added to them, so you would have to be very confused indeed not to realise what they’re for.) Hong Kong postbox fanciers say that the insignias are “part of Hong Kong’s heritage and daily life”, and plan to protest on Saturday.

So are they right? At what point does a bitter colonial history stop needing to be expunged and become, well, just history, that needs actual preservation? Look around the world and you’ll find few clear answers. For instance, postbox fanciers aside, Hong Kong could probably get by without 59 royal insignias. It could also probably get by without the four gas lamps on Duddell Street, except they have become something of a landmark now, so it is not worth the trouble of removing them.

Try to rid Hong Kong of its (originally British) double-decker trams, however, and you would have a real fight on your hands. Over the years, as well as helping people get around, the “ding-dings” have become emblematic of the territory, and are now an important tourist attraction. Indeed Hong Kong Tramways still operates several beautifully preserved “antique” trams.

The people of Kolkata might feel the same about their trams too, which are also relics of a colonial past. Before Indian independence, trams were often attacked as a symbol of British rule, but now several have been restored and turned into restaurants – as one has in Melbourne too. What is really going on here, one might suspect, is not a sudden attack of fondness for the empire, but a growing fondness for trams, after they were phased out by most former colonial cities.

Of course the most visible vestiges of empire are its buildings, which are often not worth the trouble of replacing. Some, like the Watson’s Hotel in Mumbai, fall into disrepair, but others are cherished. The Victoria Memorial in Kolkata, built to honour India’s British empress, is now a museum and gallery. Really it comes down to the passage of time. After all, you will not find many British people with a burning desire to dismantle the remaining Norman castles and Roman villas that are our own colonial heritage.

Also, buildings and trams are useful – as are gaslights, up to a point. But when something is meant to be symbolic, such as those insignias, people do tend to want it to symbolise the right thing. Hence the changing of Calcutta to Kolkata and Madras to Chennai. The people of New Zealand will vote next month on which of four new union jackless flags they would like best to represent their country. Next year the winner will go head-to-head in a second referendum against the old one. Canada did something similar in 1965. Those Britons who do yearn for their nation’s old influence can at least take comfort from the continuing popularity of rugby and cricket – at the price of our past colonies enjoying perpetual revenge …