Junction box outside?

[#1]

'It might have been used as a connection point between external and internal cables which went to the master socket.'

Except the OP says there is no other telecoms equipment in the property.

[#2]

Those picture look much similiar to my mate in Ketley as Openreach come out and put it inside instead of outside with few hour underground work to put cable in a small duct. But he ended up pay Openreach £169 charge.

[#3]

Looking at the pictures.

The black Openreach box is used for extending and/or repair of incoming phone line drop cable, one of these

 https://www.ebay.co.uk/itm/234184402449 

If the line is being tested and found to be live would suggest there is a master socket somewhere, I'm wondering if that is inside the white box.

[#4]

@jab1  I would agree with @mystreet1  that it is a wall box with a plain blanking plate, you can clearly see the screw heads on the front and paint remnants on the back edge where it has been pulled off the wall. As for what it was connected to, can't say but if the OP says there is nothing inside the property one can only assume that whatever was there has been removed or as you thought the master socket may have been in the porch.

However @Dan_the_Van  has made a very good point, the box may well have the master socket in it and it has been covered up with the blanking plate.

[#5]

Cheers, @Dan_the_Van - I should have known about the 'black box', and I suspect the white box is an old-style master socket.

[#6]

Thank you for all your replies, after doing more investigation there is another picture in my album which I took from Google maps of the property.. My house is the one on the left and you can see where the line was previously running to the porch (which no longer exists).
Update, openreach are due to visit on 9th December to install new line, however there is a line, so I guess it'll be a case of running it inside the property..

[#7]

@Ro_s Installing a new line is fine, they will look at what cabling exists and reuse if appropriate and/or run new.

I had a "new line" installed (alongside an existing one) and they used a spare pair in the overhead wire to my house then ran a new cable down from the junction at the eaves to a new master socket.

I prepared by drilling a hole through the wall in advance to exactly where I wanted the new socket to be; the engineer was very happy to use it.