The authors prove a characterisation of the classical unital that is a generalisation of a characterisation proved in 1982 by Lefevre-Peresy. It is shown that if \({\mathcal U}\) is a Buekenhout-Metz unital with respect to a line \(\ell_\infty\) in \(\text{PG}(2,q^2)\) such that a line of \(\text{PG}(2,q^2)\) not through \({\mathcal U}\cap \ell_\infty\) meets \({\mathcal U}\) in a Baer subline, then \({\mathcal U}\) is classical. An immediate corollary is that if \({\mathcal U}\) is unital in \(\text{PG} (2,q^2)\) such that \({\mathcal U}\) is Buekenhout-Metz with respect to two distinct lines, then \({\mathcal U}\) is classical.