"plain as Salisbury" meaning in English

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "Salisbury Plain"
      },
      "expansion": "Salisbury Plain",
      "name": "m"
    }
  ],
  "etymology_text": "Presumably a pun on Salisbury Plain, or perhaps in reference to the spire of Salisbury Cathedral, which can be seen at a distance.",
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "plain as Salisbury (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "British English",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English similes",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "ref": "1893, Egerton Castle, Consequences, page 248",
          "text": "If I can't show you I've come by them honestly, perhaps you'd rather not have them, though, if nicely cooked and dished up, I'll be bound they can be made to prove, as plain as Salisbury, that you've no more right to the estate — nor to the name of Kerr, for all that — than that gentleman yonder.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "Synonym of plain as day."
      ],
      "id": "en-plain_as_Salisbury-en-adj-Og67O6YJ",
      "links": [
        [
          "plain as day",
          "plain as day#English"
        ]
      ],
      "qualifier": "simile",
      "raw_glosses": [
        "(UK, simile, informal, dated) Synonym of plain as day."
      ],
      "synonyms": [
        {
          "tags": [
            "synonym",
            "synonym-of"
          ],
          "word": "plain as day"
        }
      ],
      "tags": [
        "UK",
        "dated",
        "informal",
        "not-comparable"
      ]
    }
  ],
  "word": "plain as Salisbury"
}

{
  "etymology_templates": [
    {
      "args": {
        "1": "en",
        "2": "Salisbury Plain"
      },
      "expansion": "Salisbury Plain",
      "name": "m"
    }
  ],
  "etymology_text": "Presumably a pun on Salisbury Plain, or perhaps in reference to the spire of Salisbury Cathedral, which can be seen at a distance.",
  "head_templates": [
    {
      "args": {
        "1": "-"
      },
      "expansion": "plain as Salisbury (not comparable)",
      "name": "en-adj"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "adj",
  "senses": [
    {
      "categories": [
        "British English",
        "English adjectives",
        "English dated terms",
        "English entries with incorrect language header",
        "English informal terms",
        "English lemmas",
        "English multiword terms",
        "English similes",
        "English terms with quotations",
        "English uncomparable adjectives"
      ],
      "examples": [
        {
          "ref": "1893, Egerton Castle, Consequences, page 248",
          "text": "If I can't show you I've come by them honestly, perhaps you'd rather not have them, though, if nicely cooked and dished up, I'll be bound they can be made to prove, as plain as Salisbury, that you've no more right to the estate — nor to the name of Kerr, for all that — than that gentleman yonder.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "Synonym of plain as day."
      ],
      "links": [
        [
          "plain as day",
          "plain as day#English"
        ]
      ],
      "qualifier": "simile",
      "raw_glosses": [
        "(UK, simile, informal, dated) Synonym of plain as day."
      ],
      "synonyms": [
        {
          "tags": [
            "synonym",
            "synonym-of"
          ],
          "word": "plain as day"
        }
      ],
      "tags": [
        "UK",
        "dated",
        "informal",
        "not-comparable"
      ]
    }
  ],
  "word": "plain as Salisbury"
}