Nonsense you say? Sadiq Khan has seemed quite proudly that white British are a minority. And there is a known issue with voter fraud, bloc votes and abuse of postal voting among certain communities, particularly Bangladeshi and Pakistani origin.
Census data.
Demographics of London
Major ethnic
White: 53.8% (2021) White British: 36.8% (2021)
Minor ethnic
Asian British: 20.8% (2021) Black British: 13.5% (2021) Mixed: 5.7% (2021) Other: 6.3% (2021)
Language
Spoken
British English (main language: 78.4%)
From the article linked below:
Several reports have highlighted that, within Britain, allegations of electoral fraud tend to be more common in areas with large Pakistani and Bangladeshi communities. However, the extent of this association has not yet been quantified. Using data at the local authority level, this paper shows that percentage Pakistani and Bangladeshi (logged) is a robust predictor of two measures of electoral fraud allegations: one based on designations by the Electoral Commission, and one based on police enquiries. Indeed, the association persists after controlling for other minority shares, demographic characteristics, socio-economic deprivation, and anti-immigration attitudes. I interpret this finding with reference to the growing literature on consanguinity (cousin marriage) and corruption. Rates of cousin marriage tend to be high in countries such as Pakistan and Bangladesh, which may have fostered norms of nepotism and in-group favoritism that persist over time. To bolster my interpretation, I use individual level survey data to show that, within Europe, migrants from countries with high rates of cousin marriage are more likely to say that family should be one's main priority in life, and are less likely to say it is wrong for a public official to request a bribe.
https://www.sciencedirect.com/science/article/abs/pii/S0261379417300811