Prolific pen use from all suspects. We have seen 3 out of the four suspects clearly using fountain pens
Episode 1: Dean on his mothers day card and Fiona during a counselling session with a young woman.
Episode 2: Liz was writing in a notebook when her mum called her but nib was unclear. Ram was using a pen with a lid but couldn't see the nib when his boss came into his office. Fiona signing a contract for the loan.
Episode 3: Ram using a pen when in his office when Sunny arrived at his police station and reception called his office, again nib was unclear.
Episode 4: Ian Henderson the police trainer was questioned in the snooker club when he was describing Liz it cut to a scene of her sitting at a desk crossing out a line of a document with a fountain pen.
So Dean, Fiona and Liz defiantly have fountain pens. Ram could have one but unclear. If the fountain pens were a passing out gift within the group the fifth person who would have also had one is Rob Foggarty who is dead.
I think Ram is too obvious a suspect even though Fiona's statement seems to implicate him. Given the fact Ram had already had an altercation with the victim Walsh and came off worse would he be brave enough to fight with him on his own again?
According to Fiona Dean was the only one who was very calm that night and walked after Ram and Rob. He could have stumbled across Walsh before the others and done it. They knew him as nice quiet Dean, If Ram and Rob came across what he had done they would most likely believe it was an accident if he told them and it would explain why Ram was giving Walsh CPR when Fiona found them. In his conversation with his wife he said said how much he hated his family and their values and the person they nearly made him become, how it had been a long hard 30 years and how he begged her to please not let him go back there.
Also the pens sound like the type of gift that Liz would purchase as an academic so she could easily replace hers if she used her first one to kill Walsh. Fiona was a heavy drinker so her timings might be off. It may only have been a few minutes before her and Liz left the car and Fiona even admitted they split up to find the others. Liz could have found him first and snapped - she has shown when pushed she can be threatening. Then left the allotment for Ram to find him.
Ram sounds as if he was the main person to cover it up because of his previous fight with Walsh so he was in self preservation mode, that doesn't necessarily make him the killer. I do wonder why his father won't talk to him though.
Sorry for the essay