Prisoners' rights campaigners have reacted with astonishment to the hush-hush transfer of Oluwaseni Olusanmokun from Stanley Prison to one in his home country, Nigeria. Olusanmokun, 21, the son of the Nigerian Consul-General to Hong Kong, Ebenezer Olusanmokun, was jailed for two years in September after being found guilty of wounding a police inspector and being in possession of a stun gun without a licence. Letters to security officials from another Nigerian prisoner reveal that similar requests for a transfer are frustrated at every turn. Alan Crawley, an executive board member of the Prisoners Friends' Association, said: 'It's certainly very unfair. Just last Friday I was dealing with a Nigerian who is serving 23 years for smuggling 6kg of heroin. He just wants to be back home and close to his relatives.' Hong Kong has signed agreements with Britain, the United States, Thailand and Sri Lanka to transfer prisoners. Four inmates have since been returned to their home countries to serve out their sentences. A Security Bureau spokesman said: 'There have been four cases of outward transfers to the UK and one case of inward transfer from the US. 'The amount of time needed for the processing of an application depends on the efforts of both the receiving and transferring jurisdictions and varies from case to case. 'Of the aforementioned five cases, the process took a period ranging from 10 to 31 months.' Olusanmokun's transfer took just 2.5 months from the date of his conviction. A diplomatic source said: 'Some sort of deal must have been done. These things usually take months.' Mr Crawley added: 'To be fair, I don't think the Hong Kong Government treats people any differently. I think they genuinely have a problem with co-operation with Nigeria. 'A diplomat son's name gets put forward and suddenly things may have happened at the Nigerian end.' The Security Bureau says it has to be satisfied that the Hong Kong sentence will be enforced but it is not known if any follow-up checks have been carried out on Olusanmokun.