> It's not long enough to be a London telephone number, and, today, I think London numbers start with 020.

I used to work with telephony until 2011. While I worked in Sweden, I am sure this applies for UK, too.

There is no standard in phone number lengths, you can have all sorts of prefixed series, so for example if the area code is "1", then the number 0 could be routed to a destination.

So 04410 is theoretically valid.

Back then we even had 3-digit short form numbers (like 911) that we had to specifically deal with each phone operator for keeping.

It was used for pricey phone dating.