areas of Montmartre and Gare Saint-Lazare in the north with Montparnasse and Vaugirard in the south. The line would establish a second north–south transport axis of the city, west of the existing line four. Berlier's design of two deep, parallel, iron-lined tunnels was modelled on the London Underground system. This method allowed the straightest line possible to be built, without passing underneath buildings and free from interference with underground sewers. The City Council liked the plan and on 28 December 1901 granted the tender for a Montparnasse-Montmartre line to Messrs Janicot and Berlier. In June 1902, a new company, new competitor of the "Parisian Metropolitan Rail Company" (CMP), was established : the Nord-Sud Company (in French ). The grant to build what would become Line A was transferred to the Nord-Sud Company; which was approved on 26 March 1907. While the infrastructure of the CMP was financed by the city corporation, Nord-Sud project was the sole responsibility of the Nord-Sud Company. The link between two important but distant urban centres guaranteed heavy traffic for the line and it would also directly compete with the CMP and tramway companies, threatening their monopoly across the city. The City was wary of inciting new demands to license other lines, and of eventually provoking industrial disorder, something already experienced on the tramway network. French law required a Déclaration d'utilité publique ("Declaration of Public Utility"), a statement of the project's public benefit before municipal construction, the concerns meant that it was not promulgated for the line until 3 April 1905. The law announced the creation "of [] public utility, of local interest, this establishment, in Paris, of a railroad, electrically powered, dedicated to the transport of passengers and their hand-luggage, from Montmartre to Montparnasse". The law became active on 19 July 1905, the southern terminus was at Porte de Versailles, long, with a northern branch from Gare St. Lazare to Porte de Saint-Quen. On 10 April 1908, the northern extension from Place des Abbesses to Place Jules Joffrin, long, was in turn authorised, followed by the final section to Porte de la Chapelle () on 24 January 1912. Construction and opening (1907–1910) The boggy undersoil of Paris made it impossible for the engineers to follow their initial concept of deeply excavated, metal-lined tunnels: digging deeper to more stable ground would raise costs. The line was finally established immediately underneath the streets using the cut and