Doing a Brierley
'Doing a Brierley' is the process of walking up the stairs with the intent of getting something, forgetting what you needed, walking back downstairs and then half the way down the stairs, remembering what you needed.
"Why did it take so long for you to get your phone?"
"Sorry, did a brierley"
or
"God! You keep doing a brierley!"
"Sorry, did a brierley"
or
"God! You keep doing a brierley!"