NY wrote
Rod Speed wrote

I dont bother to preheat electric ovens except
when cooking pizzas, the oven heats up quickly
enough so that it makes no difference in practice.

Our electric fan oven takes about 10 minutes until the element switches
off when it gets to 180-200 deg C. When cooking something with a total
cooking time (assuming hot oven) of 30 minutes, that's a significant
allowance you have to make to cooking time if you cook from cold rather
than from pre-heated.

Thats an illusion. You'll find that even with something as
small as a single frozen pie, the total time before the pie
is fine to eat is about the same time with the pie in the
oven with a preheated oven and when you put the pie in
the oven when you turn it on. So you save the preheat time.

Not true with a pizza, but thats the only common exception.

My wife always cooks from cold and adds some indefinable extra time

I dont add any extra time at all and it always works fine
with small stuff like pies.

whereas I like to get the oven at the required temp and cook for the
required time.

You'' find its the same time even with light stuff like a
single pie or some sausage rolls, enough for one person.

It does with pizzas because they are best done in
a stinking hot oven and it does take a while to get
an electric oven that hot, and the pizza itself heats
up quite quickly and cooks very quickly too, but there
isnt much else that is cooked in an oven like that.

Do they still use gas marks rather than degrees Celsius in gas ovens? I
haven't seen an explanation why gas ovens use these arbitrary numbers
rather than degrees (Fahrenheit or Celsius),

Basically because thats how they work, what you set
is the valve position, there is no thermostat like there
is with an electric oven. And there isnt that much that
needs the oven temp set very accurately to cook it
properly either, its really just a few basic temps,
stinking hot, very hot, quite hot, quite cool, barely
warm for bread raising etc.

though I have some ideas why it might have happened.

Its pretty obvious really given how gas ovens work.

I've never come across a gas cooker with an oven which doesn't have a
thermostat and which relies on a constant flow of gas no matter whether
the oven is cold or up to temp. Even my mum's old 1962 cooker gave a big
flame when you lit it, which reduced to a smaller flame when the oven was
up to temperature.

Sure, but that wasnt done with a thermostat.

I'm not sure whether the temperature sensor reduced the gas flow to a
constant intermediate value when the oven was at temp,

Not in the thermostat sense, it basically reduces
the gas flow as the temperature increases.

or whether it activated an all-or-nothing control as for an electric
cooker, where the element either runs at full power or not at all, with
the duty cycle varying according to the temperature needed.

Thats not possible with the traditional gas
oven which has no electronics involved at all.

If the oven had had a glass door I could have watched what the flame did
over time, without opening the door and changing the very thing I was
trying to watch.