This is the 1905 Act that Churchill supported. It sums up very nicely the British mindset.
By 1905, sixty per cent of all ‘aliens’ (i.e. Jewish immigrants) lived in London, and tended to live close to each other so as to form their own distinct communities. By living close to others from the same background and in similar circumstances, the incentive to assimilate with the host population was thereby diminished. This created the impression of, so to speak, an ‘alien invasion’ detrimental to the indigenous population: it was argued that the aliens were able to pay higher rents (thus causing a general inflation of rent prices) because of their greater willingness to ‘crowd together’; as a consequence of this overcrowding, the presence of immigrants was associated with disease and squalor; it was argued that they were willing to work longer and for less pay, thereby driving down the conditions and wages for indigenous workers; and it was also argued that the aliens had customs, language, ways of dressing, religion, morals and mores which were incompatible with the British way of life. A further trait of these Jewish immigrants, perhaps unique to the circumstances of the time, was their perceived political persuasions; they tended to be of a socialist or anarchist disposition, values considered antithetical to traditional British ‘liberalism’, intensifying and consolidating the image of the immigrant as holding on to a cultural outlook irreconcilable with British customs. The culmination of all these factors, specifically, opposition from the working class on the grounds of competition in the labour market, opposition from the middle classes on political grounds, and the generally perceived differences of culture and way of life, were to see the 1905 Aliens Act put into place with the explicit purpose of restricting and controlling economic migration to the UK. In brief, a convergence of elite and working class opinion paved way for a tough stance on immigration.