I have been wondering about the accent on the e of lès
In the formal spelling of Thèzan lès Béziers .
The dictionary yielded nothing.

We were fortunate to have Sile’s sister and her husband, Padraic de Bhaldraithe
Staying over the weekend and I laid the query firmly on Padraic’s lap.
(Him being the son of Ireland’s great lexicographer)

Padraic took the question to a French academic friend of his and got the following and very satisfying reply.

Bonjour,
En fait, c’est de l’ancien français et ça s’écrivait autrefois ‘lez’ et ça
veut dire ‘près de’, ‘à côté de’.

The accent was of great importance, the lès indicating that the village close to Béziers and has, as I suspected nothing to do with the plural of the definite article.

Many thanks to Padraic and to Martine Joulia for solving my little conundrum.