The research presented here constitutes the first investigation of the standard language ideology (SLI) in Great Britain that takes account of a multiethnolect -- namely Multicultural London English (MLE). A corpus-informed discourse study was conducted to explore representations of MLE and its speakers in two corpora: one containing data from non-MLE-speaking Londoners and one consisting of data from MLE speakers themselves. The data included in these corpora had been collected by means of an online questionnaire. The discourses in both corpora clearly reflected the SLI that prevails in the British context -- but much stronger evidence of this was found in the non-MLE speakers' discourses. The non-MLE speakers were also found to hold much stronger, and very negative, social stereotypes of multiethnolect speakers. There was evidence of their use of iconisation and erasure in order to create linguistic (and social) differences between themselves and MLE speakers. Given the current political climate in Great Britain, it is hypothesised that the non-MLE speakers' negative views of the multiethnolect and its speakers helped them reaffirm their own prestige, which they perceived to be threatened. Notably, the MLE speakers themselves were not complicit in the negative stereotypisation of their own group.