The Scottish Vowel Length Rule, describing lengthening of certain vowels before /r/, a voiced fricative, or a morpheme boundary, is explained on Scottish phonology. That vowel length is environmentally determined rather than being intrinsic to the vowel results in the absence from transcriptions of the relevant varieties of that quantitative contrast which is customarily applied in the description of British English vowel sets. Although a slightly recessive feature, the Rule operates widely in Scotland itself, in Orkney and Shetland, and in the accents of England bordering Scotland. It is also a factor in some forms of Northern Irish English, but not in the English of the Irish Republic.

Undoubtedly the most marked absence of contrast in the British Isles vocalic system is that of TRAP and BATH in Scotland and Northern England, and in some instances of accents in Ireland, Wales, and Orkney and Shetland. Both are typically at the low front position, or slightly retracted from it: so distinct a marker of northernness is this feature that in Northern and northern West Midland England those speakers whose accent converges on RP are nevertheless most unlikely to abandon it, so that it is necessary to include BATH [a] in the RP inventory in order to avoid any judgement of Southern bias in what is in essence a regionless accent.

FOOT/GOOSE merger is a feature of Scotland, Orkney and Shetland, and of some Northern Irish accents associated with Scotland through settlement. The merger is also a feature of Northern and West Midland English accents outside the Northeast, for a very limited set of lexical items and essentially amongst older speakers. LOT and THOUGHT also merge in Scotland, Orkney and Shetland, and this phenomenon can be found in some conservative Rural Irish accents too. Some merger of LOT and STRUT on [ɒ] is encountered in the West Midlands.

In Northern England, homophony occurs between NURSE and SQUARE in Liverpool, where both sets can be rendered with [ε:] or [з:], and, to the extent that NURSE is variably rendered [ε:], in the Hull and Middlesbrough areas of the east of the region. Whilst NEAR and SQUARE are distinct sets in the south of the East Anglia area, they merge on [e:/ ε:] in the northern part, and they are at times homophonous in the West Midlands on [ɪə/εə].