I agree it's a meaningless announcement. I was taught entirely in metric, but I buy milk and beer in pints, I measure long distances in miles and I know my waist size in inches but not in centimetres (and inches is a smaller number which is better!).
But the most commonly quoted example of people wishing to return to metric involves buying food. I don't think I've ever bought cheese by the pound or kilo - I want a piece 'about that big'. And I don't buy half a pound of sausages, I buy four or six.
If I'm forced to buy food by the pound I will leave the UK. The use of imperial is one of the reasons I stay out of the USA (along with gun, car, tips, nonexistent annual leave, exceptionalism, etc.).
I buy pasta by the kg. I buy meat by the kg. I buy carrot by the kg. I buy rice by the kg. I buy juice by the L. I can't remember all the different fractions between the imperial units and can only memorise 1 lb = 454 g (1/2 lb = 227 g; 1/4 lb = 113 g) and 1 pint = 568 mL. I will need to use a calculator if different units are used.
And for the imperial lengths, what I know is only that 1 mile = 1609 m (approximately 8/5 km for simple conversion); 1 yard = 91.44 m (approximately 10/11 m for simple conversion); and although not imperial, 1 nautical mile = 1852 m (approximately 50/27 km based on the original definition). However, despite the road sign showing miles I am still uncomfortable with them because the numbers are so small to what I normally use in elsewhere in the world. For example, the road sign on the A338 near Bournemouth Hospital shows Southampton as 28 (miles), which is actually 45 km. I have an idea what 5, 25 or 100 km is about (5 km is the typical urban distance between nearby urban districts, 25 km is the typical distance between the city centre and outer suburbs, 100 km is the approximate distance between Kowloon and Guangzhou)
In terms of speed limit, 40 mph is one which I find it difficult to judge as the metric equivalent is 64 km/h, which is a bit less than 70 km/h so I have to drive the car a bit slower than on a 70 km/h main road (in Hong Kong, speed limits are 30, 50 (default), 70, 80, 100 and 110 km/h which was converted from 20, 30, 40, 50, 60 and 70 mph in the imperial era - note that 60 km/h and 90 km/h limits don't exist in Hong Kong exactly because of this reason - however, in Ireland, 40 mph roads are converted to 60 km/h instead of 70 km/h in Hong Kong).
That said, in the UK there are certainly two obvious areas, rail being one and horse racing another, where Imperial is established and unlikely to change. It can be just as bad in aviation when you get kgs / litres / lbs / US / UK gallons for fuel quantity and conversions are required
What's the problem of horse racing? Horse racing elsewhere has already been metricated with race distances being multiples of 200 m. I have absolutely no idea what those legacy units are in horse racing.
Knots are used more commonly since the nautical mile has a direct relationship to celestial navigation and latitude and longitude.
It's a sad reality that decimal angle has never become widespread. The km has a direct relationship to celestial navigation if the latitude and longitude is specified in grads. This is probably because Britain was still the strongest maritime nation in the world when the French tried to promote decimal angle, which failed against British influence except in some specialised applications.
If grads replaced decimal angles in nautical navigation, the use of nautical miles would have been disappeared and km would be used.
The style guide is reasonable, but some of the rest of the document reads like a bunch of metric zealots.
I quote: "Measuring fuel consumption in miles per gallon is of no value when fuel is sold in litres." It does have value. For example, 50 mpg is better than 40 mpg. This is true irrespective of the units the fuel was sold in. The only time I do a litres to gallons conversion is to assess the accuracy of the car's metering, which is only needed once per car.
Measuring fuel consumption in miles per gallon is really having no value when fuel is sold in litres. If the car is quoted as 50 mpg, I have no idea at all how many litres of fuel I will need to make a 100-mile journey unless I make a conversion to gallon (a unit which I have no idea what it is) to litres. The fact that a 50 mpg car is better than a 40 mpg car is meaningless except at the moment we want to buy / replace cars because when we drive we are interested in how much fuel I will need.
For example, I owned a motorcycle in the past. It is a very basic one with no fuel consumption metering. Each time I refueled it I write the odometer reading on the fuel slip such that, over time, I know the fuel consumption of it, which automatically comes out as L / km (it was in Hong Kong with metricated motoring) - two decimal places away from the industrial-standard L / 100 km values. Therefore, in Britain, as fuels are sold in L and odometer reading in miles, the figure will be L / mile which is a useful measure for direct calculation of how much fuel I will need. There is absolutely no reason to use gallons here.
