London's telephone code is 020 followed by an eight digit number which will start with 3,7 or 8. The number that you have asked about is not a London number as you have described it.
This is an inner London number.
The country code and area code of Svenstavik, Sweden is 46, (0)687.
The country code and area code of Lifou, New Caledonia is 687, 45.
The country code and area code of Belep, New Caledonia is 687, 42.
The country code and area code of Boulouparis, New Caledonia is 687, 35.
The country code and area code of Adolfo Ruiz Cortines, Mexico is 52, (01)687.
The telephone country code for Zimbabwe is +263. The area code for Sanyati is 0687, or +263 687 in international format.
This isn't a London code. It is the area code for Brentwood in Essex which is about 30 miles northeast of London.
The country code and area code of East London, South Africa is 27, (0)43.
London is area code 020.
In the UK, area code 020 is London. There is no area code 0208.
Bromley is covered by the area code for London, which is 020.