(1)Where any person is returned to the United Kingdom by a foreign state in pursuance of extradition arrangements, he shall not, unless he has first been restored or had an opportunity of leaving the United Kingdom, be triable or tried for any offence committed prior to the surrender in any part of the United Kingdom, other than—
(a)an offence in respect of which he was returned; or
(b)any offence disclosed by the particulars furnished to the foreign state on which his return is grounded; or
(c)any other offence in respect of which the foreign state may consent to his being tried.
(2)Where any person returned to the United Kingdom in pursuance of extradition arrangements has been convicted before his return of an offence for which his return was not granted, any punishment for that offence shall by operation of this section be remitted; but his conviction for it shall be treated as a conviction for all other purposes.