Bit of an unknown - unknown artist, unknown date. Somewhat stereotypical image of London - Tower Bridge, a 'Bobby' and a couple of soldiers, for once not wearing bearskins. The poster is from Chemins de Fer de l'Ouest and mentions the London, Brighton & South Coast Railway.
These participating companies date the poster between 1855 and 1909, the dates of the Compagnie des Chemins de Fer de l'Ouest. The LB&SCR existed between 1846 and 1922. The image looks distinctly Victorian.
The poster promotes the route from Gare St Lazare via Dieppe-Newhaven. That route may have been a tad slow but it was cheap ('Route Economique'). See also London-Paris via Newhaven-Dieppe.
Keywords: Paris; London; Londres; Gare St Lazare; Chemins de Fer de l'Ouest; London, Brighton & South Coast Railway; Edwardian; Bobby; Tower Bridge; LB&SCR; Chemin de Fer de l'Etat; Dieppe; Newhaven