Terry Addison has found clay courts difficult, recording 13–34 across 47 matches (27.7%). The numbers point to a surface that has not consistently suited the game — a key area of opportunity on the calendar.

At Grand Slam level (Roland Garros): Terry Addison is 2–3 (40.0%) across 5 Grand Slam matches — below .500, though the elite draw depth at the Slams makes that a notoriously difficult barrier to crack.

By format on clay — best-of-five: 3–7 (30.0%); best-of-three: 10–27 (27.0%). Slightly better in five-set matches on clay — a positive sign for the Slams specifically.

Best season: 1969 — 4–5 (44.4%) from 9 matches. The best single-season display to date — a useful reference point as the clay record continues to develop.