  We present the results of our study on three close pairs of QSOs. Our results
are consistent with the existence of a proximity effect due to the foreground
QSO, but due to its weakness we can only reject the absence of such effect at
approx. 1 sigma level. By modelling this proximity effect in terms of a simple
photoionisation model, we find the best value for the UV ionizing background to
be approx. 10**(-20.5) erg cm**(-2) s**(-1) Hz**(-1) srad**(-1) at the Lyman
limit, and an absolute lower limit (95\% confidence) of 10**(-21.8) in the same
units. This lower limit rejects a number of models for the UV background where
it is mostly contributed by QSOs and absorption by Lyman limit systems is taken
into account.
