On hoardings in the tube and elsewhere Londoners are being treated to a poster that includes the two IPA symbols ɛ and ɔ (aka cardinals 3 and 6).
As you see, the poster includes the lines Biɛ Wɔshwɛɔɔ and Yɛ. You can read more about it here.
The characters ɛ (U+025B) and ɔ (U+0254) are used in the orthography of various Ghanaian languages. The one we have here is presumably Akan (a cover name for Twi and the mutually intelligible Fante), spoken by about 19 million people, half in Ghana and half elsewhere. As you might expect, these symbols stand for the lax mid vowels, front unrounded and back rounded respectively. (There is a system of vowel harmony. Phonologists classify these two vowels as [-ATR], as opposed to their [+ATR] counterparts e and o.)
The IPA does not distinguish upper and lower case, although the Latin alphabet used for orthographies does. So Twi also makes use of the special upper-case characters Ɛ (U+0190) and Ɔ (U+0186).
Probably most of the Londoners who see this poster imagine that these special letters, if they notice them at all, are just fancy ways of writing ordinary e and o. Phoneticians and Africanists know better.