Converting cell array to double?

How can I convert the cell array A into the column vector B? (Deleting the letter B and leading white spaces)

A = { 'B 1'; 'B 12'; 'B123' }

B = [ 1; 12; 123 ]

Answer 1

[Azzi Abdelmalek]

A = { 'B 1'; 'B 12'; 'B123' }
B=str2double(regexp(A,'\d+','match','once'))