As for Thursday, 22 June 2021, the letter which has taken the longest to return is that of Pitcairn; the round trip at the time of its return was 664 days (despite being franked on 15 November 2020).
| Territory | Post Address | Letter Mailed | Letter Returned | Days Elapsed | Note |
|---|---|---|---|---|---|
| Akrotiri and Dhekelia | 12345678 LCPL B Jones B Company 1 Loamshire Regt Dhekelia BFPO 58 GB United Kingdom | 8/28/2019 | 11/13/2019 | 77 | |
| Akrotiri and Dhekelia | 12345678 LCPL B Jones B Company 1 Loamshire Regt Dhekelia BFPO 58 GB United Kingdom | 8/28/2019 | 1/3/2020 | 128 | |
| Anguilla | N. Guem 27 Back St The Valley 2640 Anguilla | 8/28/2019 | 11/29/2019 | 93 | |
| Bermuda | N. Guem 27 Back St Hamilton HM 12 Bermuda | 8/28/2019 | 10/25/2019 | 58 | |
| British Antarctic Territory | N. Guem Port Lockroy Goudier Island BIQQ 1ZZ British Antarctic Territory | 8/28/2019 | 7/2/2020 | 309 | |
| British Antarctic Territory | N. Guem UKAHT – Port Lockroy c/o Stanley Post Office Stanley Falkland Islands F1QQ 1ZZ South Atlantic Ocean | 8/28/2019 | 2/4/2020 | 160 | |
| British Indian Ocean Territory | 12345678 LR B Jones NP 1002 Diego Garcia (BIOT) BFPO 485 GB United Kingdom | 8/28/2019 | |||
| British Indian Ocean Territory | 12345678 LR B Jones NP 1002 Diego Garcia (BIOT) BF1 4TG GB United Kingdom | 8/28/2019 | |||
| British Indian Ocean Territory | N. Guem 27 Back St Diego Garcia BBND 1ZZ British Indian Ocean Territory | 8/28/2019 | 11/23/2019 | 87 | |
| British Indian Ocean Territory | N. Guem 27 Back St Diego Garcia British Indian Ocean Territory Chagos Archipelago Indian Ocean (via Singapore) | 8/28/2019 | 12/5/2019 | 99 | |
| British Indian Ocean Territory | N. Guem DIEGO GARCIA c/o Sure (Diego Garcia) Limited 3 Shenton Way Unit # 02-01 Shenton House Singapore 068805 SINGAPORE | 9/10/2019 | orig sent 8/28/2019, usps returned 9/09/2019 due to damage (9/06); 12 days rrt. resent. | ||
| British Indian Ocean Territory | N. Guem DIEGO GARCIA c/o Sure (Diego Garcia) Limited PSC 466 Box No. 59 FPO-AP 96595-0059 USA | 8/28/2019 | |||
| British Indian Ocean Territory | N. Guem 27 National Highway BBND 1ZZ Three Brothers British Indian Ocean Territory | 7/29/2019 | 12/21/2019 | 145 | |
| British Virgin Islands | N. Guem 27 Back St Road Town, Tortola, VG1110 British Virgin Islands | 8/28/2019 | |||
| Cayman Islands | N. Guem 27 Back St George Town Grand Cayman KY1-1010 Cayman Islands | 8/28/2019 | 9/16/2019 | 19 | |
| Falkland Islands | N. Guem 27 Front St Stanley FIQQ 1ZZ Falkland Islands | 8/28/2019 | 11/7/2019 | 71 | |
| Gibraltar | N. Guem 2-7 Back Square Gibraltar GX11 1AA Gibraltar | 8/28/2019 | 10/24/2019 | 57 | |
| Montserrat | N. Guem Back Point Road Brades, MSR1310 Montserrat | 8/28/2019 | 12/5/2020 | 465 | |
| Pitcairn, Henderson, Ducie and Oeno Islands | N. Guem 27 Back St Adamstown PCRN 1ZZ Pitcairn Island | 8/28/2019 | 6/22/2021 | 664 | |
| Saint Helena | N. Guem 27 Back St Jamestown STHL 1ZZ Saint Helena | 8/28/2019 | |||
| Saint Helena | N. Guem 27 Back St, Jamestown Saint Helena STHL 1ZZ South Atlantic Ocean | 8/28/2019 | |||
| Ascension Island | N. Guem 27 Back St Georgetown ASCN 1ZZ Ascension | 8/28/2019 | 9/10/2019 | 13 | usps return mark: 9/06/2019 never left usa |
| Ascension Island | N. Guem 27 Back St Georgetown, Ascension ASCN 1ZZ South Atlantic Ocean | 8/28/2019 | |||
| Tristan da Cunha | N. Guem 27 Back St Edinburgh of the Seven Seas TDCU 1ZZ Tristan da Cunha | 8/28/2019 | 2/29/2020 | 185 | |
| Tristan da Cunha | N. Guem 27 Back St Edinburgh Tristan da Cunha TDCU 1ZZ South Atlantic Ocean | 8/28/2019 | 1/26/2020 | 151 | |
| Tristan da Cunha (Inaccessible Island) | Mssrs Gustav and Frederick Stoltenhoff Port David Inaccessible Island TDCU 1ZZ Tristan da Cunha | 8/28/2019 | |||
| South Georgia and the South Sandwich Islands | N. Guem 27 Back St King Edward Point SIQQ 1ZZ South Georgia and the South Sandwich Islands | 8/28/2019 | 9/10/2019 | 13 | usps return mark: 9/06/2019 never left usa |
| South Georgia and the South Sandwich Islands | Nin Guem King Edward Point Research Station British Antarctic Survey Stanley Falkland Islands FIQQ 1ZZ South Atlantic Ocean | 8/28/2019 | 1/27/2020 | 152 | |
| Turks and Caicos Islands | N. Guem 27 Back St Cockburn Town TKCA 1ZZ Turks and Caicos Islands | 8/28/2019 |