| 1914 | [An immature female obtained at St. Leonards (ES) on 26 January (BoMNH 205392).] | WB HR |
| [An adult male obtained at Bexhill (ES) on 24 June.] | WB HR |
| 1960 | A first-summer at Langney Point (ES) on 19 and 22 June and 6 and 10 July (Harber, D.D. 1962. Slender-billed Gull in Sussex: a bird new to Britain. British Birds 55:169-71.). | *61 ×61 dFH |
| 1963 | A first-year seen at Rye Harbour Gravel Pits (ES) for an hour on 28 April (Charlwood, R.H. 1964. A second Slender-billed Gull in Sussex. British Birds 57:81-2.). | * × |