We give a method of deriving the field-strengths of all massless and massive, i.e. gauged, maximal supergravity theories in any dimension starting from the Kac-Moody algebra E11. Considering the subalgebra of E11 that acts on the fields in the non-linear realisation as a global symmetry, we show how this is promoted to a gauge symmetry enlarging the algebra by the inclusion of additional generators. Given the enlarged algebra corresponding to the massless theory, we show that this can be deformed to obtain the algebra corresponding to the gauged theory. We show how this works in detail for the case of Scherk-Schwarz reduction of IIB to nine dimensions. We then classify all the possible deformations in any dimensions and show that these are in one to one correspondence with all the possible gauged supergravities. This provides a very efficient, simple and unified derivation of the field strengths and gauge transformations of all the bosonic fields of any maximal supergravity theory.