The London Houses of Parliament crop up regularly in Monet's work in 1900. At first the artist observed them from the terrace of St Thomas Hospital, on the opposite bank, near Westminster Bridge. Monet's London production, which includes views of Charing Cross bridge and Waterloo bridge, is in fact dominated by variations in the light and atmosphere due to the famous London fog, which enveloped the city, especially in autumn and winter. The unreal ghostly outline of Parliament buildings looms up like an apparition. The stone architecture seems to have lost its substance. Sky and water are painted in the same tones, dominated by mauve and orange. The brushstrokes are systematically broken into thousands of coloured patches to render the density of the atmosphere and the mist. Paradoxically, these impalpable elements become more tangible than the evanescent building which seems to dissolve in the shadow.

https://www.musee-orsay.fr/en/artworks/londres-le-parlement-trouee-de-soleil-dans-le-brouillard-1177