A transmitter for communicating data using Orthogonal Frequency Division Multiplexed, OFDM, symbols, the OFDM symbols including a plurality of sub-carrier symbols formed in the frequency domain for modulating with the data to be carried and pilot sub-carriers and the transmitter being arranged to form a Multiple Input Multiple Output, MIMO, scheme, the transmitter including a modulator arranged in operation to receive on a first input, national broadcast data symbols from a first data pipe according to a national broadcast channel for transmission, to receive on a second input, local service data symbols from a local service insertion data pipe according to a local service channel for transmission, and to modulate the data bearing sub-carrier signals of the OFDM symbols with either the national broadcast data symbols or the local service data symbols and the national broadcast data symbols, the modulation of the data bearing sub-carrier signals of the OFDM symbols with the national broadcast data symbols being performed by mapping the data symbols according to a first modulation scheme, and the modulation of the sub-carrier signals of the OFDM symbols with the local service data symbols and the national broadcast data symbols being performed by mapping the national broadcast data symbols and the local service data symbols according to a second modulation scheme, a MIMO encoder arranged to receive the OFDM symbols and to form at least first and second versions of the OFDM symbols, a frequency interleaver arranged to receive the first and second versions of the OFDM symbols and to interleave the position of the respective modulated sub-carriers; and a pilot signal inserter arranged to receive the first and second version of the OFDM symbols and to insert first pilot symbols at the pilot sub-carriers of the first version of the OFDM symbols and second pilot symbols at the pilot sub-carriers of the second version of the OFDM symbols; a radio frequency modulator which is arranged to modulate a radio frequency carrier signal with the first and second versions of the OFDM symbols for transmission via first and second antennas respectively, wherein the first modulation scheme is a lower order modulation scheme providing first modulation symbols with values from a smaller number of constellation points in the complex plane than the second modulation scheme which is a higher order modulation scheme, the second modulation scheme providing second modulation symbols with values which are disposed in the complex plane about corresponding values of the first modulation scheme, with the effect that detection of one of the second modulation symbols of the second modulation scheme will provide the local insertion data symbols and the national broadcast data symbols and allow detection of national broadcast modulation symbols from the first modulation scheme providing the national broadcast data symbols, in the presence of modulation symbols from the second modulation scheme, characterized by, if the modulator is arranged to modulate the data bearing sub-carriers with both the local service data symbols and the national broadcast data symbols, the transmitter is arranged to to generate local pilot symbols at predetermined locations within the first and second OFDM symbols, to de-interleave the local pilot symbols from the locations within the first and second OFDM symbols, the de-interleaving being a reverse mapping of the interleaving performed by the frequency interleaver, and to include the local pilot symbols with the local service data symbols at the locations determined by the de-interleaving.