In 1937 they were invited to exhibit their work at the gallery of Lund Humphreys and because they liked London they decided to stay. They were key figures in the influx of artistic talent arriving in Britain from the rest of Europe at that time, under the impetus of the threat of persecution by the Nazis and the imminent prospect of war.

During the 21 years of their collaboration they produced work of outstanding originality and quality. Their first children's book Lokomotywa, or the Locomotive, published in Poland in 1934,  is generally considered a masterpiece. Faber and Faber commissioned Lewitt-Him to illustrate The Little Red Engine gets a Name by Diana Ross (1942), which is a classic of its period.

During World War II Lewitt-Him worked for the British Ministry of Information, the Post Office, the Ministry of Food and others, also for the Polish and Dutch Governments in exile producing mainly posters. These were ahead of their time, distinguished, vivacious and witty. The Vegatabull and Shank's Pony are still remembered.

Shortly after World War 2, the Lewitt-Him Partnership contributed to the "Britain can make it" exhibition of 1946 and to the Festival of Britain (1951)  designing murals for the Education Pavilion and the Guiness Festival Clock in Battersea Park.