Upton's system for representing the vowels of British English is based on the International Phonetic Alphabet, following the normal practice of the late 20th century. He chose a presentation of these known as "qualitative–quantitative," where vowels are distinguished and represented in transcription by both quantity (length) and quality (distinct symbols for the vowel sounds). Short vowels and long vowels are represented by specific symbols, while long vowels are also followed by /ː/, a colon-like mark used in IPA to indicate their greater length.
The IPA symbols he chose for BET, BAT, NURSE, SQUARE, and PRICE of British English are different from those found in other dictionaries. To some extent this reflects actual shifts in the "Received Pronunciation" of British English during the 20th century. Some British linguists accustomed to a different set of symbols have taken issue with some of his choices. One such linguist is John C. Wells.