A streamlined windscreen wiper comprises a longitudinal wiper blade, fairing comprising a central mounting and at least one end cap, at least one adapter element fixed to the central mounting which comprises a central web and two legs, one of said at least one end caps being articulated to said adapter element, and a retention means comprising a first portion formed in said adapter element and engaging a complementary second portion extending from a lower surface of the central mounting, the first portion of the retention means comprises a tongue extending from the central web of the adapter element at a longitudinal extremity thereof.