back on topic though you may well be star wired somewhere, the 4 wire pictures is not exactly brand new so star wiring would be expected.
the extension going by the fact its 6 wire rather than 4 wire would point at that being a later addition.
just follow the cables either inside going around the house or from outside heading in. you will find it eventually. be carefull though as its before the master it would be considered openreachs network.
these comments are my own and in no way represent any company that i may or may not be linked too.