SELECT sum(total_pounds) FROM purchase AS T1 JOIN branch AS T2 ON T1.branch_id  =  T2.branch_id WHERE T2.city  =  'London' AND T1.year  =  2018
SELECT sum(total_pounds) FROM purchase AS T1 JOIN branch AS T2 ON T1.branch_id  =  T2.branch_id WHERE T2.city  =  'London' AND T1.year  =  2018 <table_name> : branch col : Branch_ID | Name | Open_year | Address_road | City | membership_amount row 1 : 1 | Alexandre | 2001 | Valleys Place | London | 112 row 2 : 2 | Popert | 2009 | Oaks Crescent | London | 11 row 3 : 3 | Stanley | 2013 | Abbott Street | London | 6 row 4 : 4 | Zytogorski | 2009 | Abbey Rise | Oxford | 7 row 5 : 5 | Cochrane | 2012 | Brampton Road | London | 1418 row 6 : 6 | Taverner | 2014 | Cecilia Avenue | Oxford | 56 row 7 : 7 | Saint Amant | 2015 | Concord Road | London | 91 row 8 : 8 | Brooke Greville | 2009 | Glebe Street | Oxford | 31 <table_name> : purchase col : Member_ID | Branch_ID | Year | Total_pounds row 1 : 1 | 3 | 2018 | 2013.32 row 2 : 2 | 5 | 2018 | 321.13 row 3 : 3 | 1 | 2017 | 988.09 row 4 : 4 | 1 | 2018 | 20.99 row 5 : 3 | 5 | 2018 | 343.76 row 6 : 6 | 6 | 2018 | 232.09 row 7 : 2 | 2 | 2018 | 402.1 row 8 : 2 | 3 | 2018 | 430.29
col : sum(total_pounds) row 1 : 3531.59