  A test of the QED process e+e- -> gamma gamma (gamma) is reported. The data
analysed were collected with the DELPHI detector in 1998 and 1999 at the
highest energies achieved at LEP, reaching 202 GeV in the centre-of-mass. The
total integrated luminosity amounts to 375.7 pb^{-1}. The differential and
total cross-sections for the process e+e- -> gamma gamma were measured, and
found to be in agreement with the QED prediction. 95% Confidence Level (C.L.)
lower limits on the QED cut-off parameters of Lambda+ > 330 GeV and Lambda- >
320 GeV were derived. A 95% C.L. lower bound on the mass of an excited electron
of 311 GeV/c^2 (for lambda_gamma = 1) was obtained. s-channel virtual graviton
exchange was searched for, resulting in 95% C.L. lower limits on the string
mass scale, M_S: M_S > 713 GeV/c^2 (lambda = 1) and M_S > 691 GeV/c^2 (lambda =
-1).
