diff --git a/intl/icu/source/data/zone/en_GB.txt b/intl/icu/source/data/zone/en_GB.txt
index aa9880b27d32..f2f22f1eaea9 100644
--- a/intl/icu/source/data/zone/en_GB.txt
+++ b/intl/icu/source/data/zone/en_GB.txt
@@ -4,9 +4,9 @@
 en_GB{
     %%Parent{"en_001"}
     zoneStrings{
-        "Europe:London"{
-            sd{"BST"}
-        }
+        // Europe/London rules implemented in code in smpdtfmt.cpp;
+        // see https://unicode-org.atlassian.net/browse/CLDR-19362 and
+        // https://unicode-org.atlassian.net/browse/CLDR-19382.
         "meta:Europe_Central"{
             sd{"CEST"}
             sg{"CET"}
diff --git a/intl/icu/source/i18n/smpdtfmt.cpp b/intl/icu/source/i18n/smpdtfmt.cpp
index 38e4dedc33e0..1e443770520a 100644
--- a/intl/icu/source/i18n/smpdtfmt.cpp
+++ b/intl/icu/source/i18n/smpdtfmt.cpp
@@ -1919,7 +1919,30 @@ SimpleDateFormat::subFormat(UnicodeString &appendTo,
                     UPRV_UNREACHABLE_EXIT;
                 }
             }
-            appendTo += zoneString;
+            // CLDR analyzes abbreviations as attaching to "standard time" and "daylight-saving time".
+            // In en-GB, however, the abbreviations for Europe/London should attach to the offset:
+            // +0: "GMT"
+            // +1: "BST" either for British Summer Time or, in the turn of the 1960s and 1970s, British Standard Time
+            // +2: "BDST" for British Double Summer Time (in the 1940s only)
+            //
+            // Do "GMT+2" instead of "BDST" at least for now on the assumption that present-day users
+            // might not recognize the historical abbreviation.
+            UnicodeString id;
+            if (zoneString == u"GMT+0" && strcmp(fLocale.getBaseName(), "en_GB") == 0 && tz.getID(id) == u"Europe/London") {
+                // Previously in upstream, +0 was formatted as "GMT" regardless of year. However, upstream
+                // started doing "GMT+0" for +0 before 1970 while keeping "GMT" for +0 for newer dates, and that turned up
+                // a Web compat issue with a British bank, so restoring "GMT" even for older dates.
+                // https://unicode-org.atlassian.net/browse/CLDR-19362
+                appendTo += u"GMT";
+            } else if (zoneString == u"GMT+1" && strcmp(fLocale.getBaseName(), "en_GB") == 0 && tz.getID(id) == u"Europe/London") {
+                // Avoid formatting +2 as "BST". This is about formatting correctness, not Web compat.
+                // The same bank form that requires +0 to be formatted as "GMT" appears not
+                // to expect a specific formatting for cases other than +0.
+                // https://unicode-org.atlassian.net/browse/CLDR-19382
+                appendTo += u"BST";
+            } else {
+                appendTo += zoneString;
+            }
         }
         break;