Duke Street Capital, the middle market buy-out company, has emerged as one of the mystery bidders for Uniq, the quoted convenience food group, and may make a £250m (€360m) offer to de-list it.

In a prelude to a full offer to take the firm private, Duke Street has established a 3.1% stake, worth around £7m at the current share price of 193p. It built up the majority of the stake yesterday.