diff --git a/templates/results.html b/templates/results.html
index 7a7259f..5426995 100644
--- a/templates/results.html
+++ b/templates/results.html
@@ -150,6 +150,7 @@
         </td>
         <td class="col-transfer" style="padding:0.6rem 0.8rem;color:#4a5568;white-space:nowrap">
           {{ row.connection_duration }}{% if row.connection_minutes < 80 %} <span title="Tight connection">⚠️</span>{% endif %}
+          <br><span style="font-size:0.75rem;color:#718096">Circle {{ row.circle_line_depart }} → STP {{ row.circle_arrive_checkin }}</span>
         </td>
         <td style="padding:0.6rem 0.8rem;font-weight:600">
           {{ row.depart_st_pancras }}
diff --git a/trip_planner.py b/trip_planner.py
index c7e3286..e732b93 100644
--- a/trip_planner.py
+++ b/trip_planner.py
@@ -9,6 +9,12 @@ MAX_GWR_MINUTES = 110
 DATE_FMT = '%Y-%m-%d'
 TIME_FMT = '%H:%M'
 
+# Circle Line: Paddington (H&C) → Kings Cross St Pancras
+CIRCLE_LINE_MINUTES_PAST = [8, 18, 28, 38, 48, 58]  # departures past each hour
+CIRCLE_LINE_JOURNEY_MINUTES = 11
+PAD_WALK_TO_UNDERGROUND_MINUTES = 8   # GWR platform → Paddington Underground
+KX_WALK_TO_CHECKIN_MINUTES = 10       # Kings Cross St Pancras platform → St Pancras check-in
+
 
 # Bristol Temple Meads → London Paddington walk-on single fares.
 # Weekday restrictions (Mon–Fri only):
@@ -45,6 +51,28 @@ def _parse_dt(date: str, time: str) -> datetime:
     return datetime.strptime(f"{date} {time}", f"{DATE_FMT} {TIME_FMT}")
 
 
+def _next_circle_line(arrive_paddington: datetime) -> tuple[datetime, datetime]:
+    """
+    Given GWR arrival at Paddington, return (circle_line_depart, arrive_checkin).
+
+    Walk 10 min to Paddington Underground, catch next Circle Line at :08/:18/:28/:38/:48/:58,
+    11 min journey to Kings Cross St Pancras, 10 min walk to St Pancras check-in.
+    """
+    earliest_board = arrive_paddington + timedelta(minutes=PAD_WALK_TO_UNDERGROUND_MINUTES)
+    minute = earliest_board.minute
+    depart_minute = next((m for m in CIRCLE_LINE_MINUTES_PAST if m >= minute), None)
+    if depart_minute is None:
+        circle_depart = (earliest_board + timedelta(hours=1)).replace(
+            minute=CIRCLE_LINE_MINUTES_PAST[0], second=0, microsecond=0
+        )
+    else:
+        circle_depart = earliest_board.replace(minute=depart_minute, second=0, microsecond=0)
+    arrive_checkin = circle_depart + timedelta(
+        minutes=CIRCLE_LINE_JOURNEY_MINUTES + KX_WALK_TO_CHECKIN_MINUTES
+    )
+    return circle_depart, arrive_checkin
+
+
 def _fmt_duration(minutes: int) -> str:
     h, m = divmod(minutes, 60)
     if h and m:
@@ -122,6 +150,7 @@ def combine_trips(
 
             total_mins = int((arr_dest - dep_bri).total_seconds() / 60)
             ticket = cheapest_gwr_ticket(gwr['depart_bristol'], travel_date)
+            circle_depart, arrive_checkin = _next_circle_line(arr_pad)
             trips.append({
                 'depart_bristol': gwr['depart_bristol'],
                 'arrive_paddington': gwr['arrive_paddington'],
@@ -129,6 +158,8 @@ def combine_trips(
                 'gwr_duration': _fmt_duration(int((arr_pad - dep_bri).total_seconds() / 60)),
                 'connection_minutes': int((dep_stp - arr_pad).total_seconds() / 60),
                 'connection_duration': _fmt_duration(int((dep_stp - arr_pad).total_seconds() / 60)),
+                'circle_line_depart': circle_depart.strftime(TIME_FMT),
+                'circle_arrive_checkin': arrive_checkin.strftime(TIME_FMT),
                 'depart_st_pancras': es['depart_st_pancras'],
                 'arrive_destination': es['arrive_destination'],
                 'train_number': es.get('train_number', ''),