Prisoners in Britain are being treated to crispy crème doughnuts and KFC as statistics reveal a 400 per cent rise in investigations of corrupt staff behaviour. A former officer claims in the new documentary UK Prisons - Sex, Drugs & Corruption that 'for every case that gets uncovered there's 10 more cases not uncovered'. Footage shows a number of videos posted to social media by prisoners with captions like 'prison take away - beautiful' and 'Chinese delivery' against the backdrop of their favourite food. Speaking to Channel 4, a recently-released prisoner called Nathan said he knew of prisoners who would bribe officers for food, phones and drugs. The former convict said: 'We call it patterning up with them.' He also highlighted some of the extortionate prices charged by officers to inmates in want of food, saying 'if she wants to say to you 500 quid and you really want it you're going to pay her 500 quid'. Nathan conceded it was an 'expensive KFC'. One video reel shared by Nathan showed a prisoner boast about their goods with a montage of food ranging from doughnuts to peri peri chicken. The clip is captioned 'that bird just keep on coming' - an apparent reference to an illicit relationship with a female prison guard who agreed to smuggle in the food. Nathan said: 'You build up a relationship with her on the wing, be flirty. Then the minute I've got your number, the question is how have I got your number? If there's text messages between me and you now you're under my thumb.' The comments are supported by data obtained via FOI that shows there were 237 cases of prison staff investigated for sexual harassment or assault between January 2022 and March 2024 There were 63 officers recommended for dismissal in same period and the figures marked an almost 400 per cent rise in investigations compared to 10 years ago. A former prison officer at HMP Onley in Rugby called Moses also told presenter David Navarro - a reformed prisoner who previously spent 10 years in jail - there were no longer army officers patrolling the building and so 'now you walk past a man's cell and it looks like a dustbin'. It comes as 44 per cent of new prison officers are under 30 and no specific qualifications are needed to take up the role. Moses, who served as a prison officer for little over half a decade as a uniformed member of staff, said officers being arrested for 'inappropriate relationships' is 'very common'. He added: 'Female prison officers get a lot of attention from male prisoners - it is bound to happen. If officers aren't strong minded they get drawn into that relationship.' A prison officer mother-of-five who had a torrid affair with an armed robber before having his baby revealed in the documentary how their sordid relationship began - only for him to end up in jail again after attacking her. Rachel Stanton, 32, entered into a relationship with Edwin Poole while he was serving a 10-and-a-half-year sentence in HMP Five Wells, Wellingborough, Northamptonshire. Her romance with Poole was uncovered when prison staff found three intimate photographs and a love letter in the inmate's cell. Stanton blamed the stress of her job for the illegal affair - and continued to deny they ever had a sexual encounter while still in prison. A Dubai cash mule, Beatrice Auty, also claimed in the documentary she was harassed by corrupt male guards when she served more than a year at HMP Bronzefield at the age of 24, the largest female prison in Europe, for her part in a £104million money laundering scheme. The poor conduct of more senior officers was also highlighted - in the aftermath of cases like that of married Victoria Laithwaite, 47, a prison governor who was caught sending prisoner James Chalmers, 30, intimate messages. The Prison Service has insisted they are introducing 'stronger vetting'. A spokesman added: 'While the vast majority of most prison staff are honest, we are catching more of the small minority who break the rules through our Counter-Corruption Unit and stronger vetting. 'Where officers fall below our high standards, we do not hesitate to take robust action.' HMP Bronzefield said they could not comment on specific cases but are 'fully committed to ensuring a safe and secure environment'. A spokesman at HMP Five Wells added they 'expect the highest standards' from employees given them 'significant support to do their jobs'.