For the professor who is working with Harrietta Lydford, how is his popularity?
research assistant refers to the student who serves for research where the abbreviation is RA; higher popularity means more popular; prof_id refers to professor’s ID;
SELECT T1.popularity FROM prof AS T1 INNER JOIN RA AS T2 ON T1.prof_id = T2.prof_id INNER JOIN student AS T3 ON T2.student_id = T3.student_id WHERE T3.f_name = 'Harrietta' AND T3.l_name = 'Lydford'