He assumed the project responsibility of important public works, without identifying himself with the political regime or with the historicist standards of the official taste of the Estado Novo and, at the same time, maintaining a critical distance in relation to the International Style orthodoxy, in search of a "third way" able to reconcile modern rationality with thoughtful consideration of the lessons of traditional architecture.

"This binomial will clearly define the practice of the architect" leading him, after his return to Portugal, to demarcate aspects of his initial work, the influence of Carlos Ramos and, even more, the historicist and regionalist constraints of the official architecture of the Estado Novo.

[4] "When, in the middle of the Salazar dictatorship, Portuguese architecture is divided between the mentors of the regime and the desire for a functionalism of an international character, [Keil do Amaral stands out] as the figure who with more energy and lucidity defends the bases for building a different perspective of work, theoretically rational and formally linked to local identities, appealing to a simple and balanced language, inspired by the continuity and the integrative sense that seems to be a constant of Portuguese architecture ".

[5] "From a formal point of view, Keil do Amaral's vast production in the 1940s, in addition to documenting contacts with the architecture of Northern Europe and the United States, translates a personal conception of spaces and volumes that transcends conceptual limitations of modernism.

Keil do Amaral will work on equipment projects and on the rearrangement of green spaces in the capital: Parque Eduardo VII; Large field; Monsanto Park.

On the eve of the beginning of the Second World War, he travels to Great Britain and Northern Ireland, France; Netherlands and Germany, to visit parks and deepen knowledge in that specific area.

Draws the central, grassy lane, flanked by a Portuguese stone sidewalk; redesigns the lake; rearranges the Greenhouse and designs the entrance close to the bank; in the eastern sector it develops a sequence of stays.

[9] Keil do Amaral's architectural production throughout the 1940s is intense; in addition to the interventions for the city parks, it designs the Lisbon Airport terminal, theaters in Mangualde and Nelas, single family homes, etc.

In March of the same year, he was elected president of the National Union of Architects, but he will be compulsorily removed by the government after only eight months, for political reasons, not even officially taking office.

In the 1960s he designed, with Carlos Manuel Ramos, Al-Shaab Stadium, Iraq, "in which a breath of renewal is felt" in its architecture that will translate into a "lightness of solution unparalleled in previous works of this type in our country".