The daughter of the murdered Russian exile Nikolai Glushkov has appealed for new witnesses to come forward and described how she discovered his body a year ago at his home in London in what she called a “trashy set up of a suicide”.

In her first media interview since his death, Natalia Glushkova told the Guardian she did not want to speculate on who might have killed her father – or why. She described him as a “charismatic and vibrant energy ball” who was positive and incapable of harming himself.

Glushkov was a prominent critic of the Kremlin and a close friend of the late oligarch Boris Berezovsky. A former executive in the Russian state airline Aeroflot, Glushkov was killed on 12 March last year at his home in New Malden. Police say he was strangled.

Natalia Glushkova. Photograph: Supplied

His murder happened a week after two Russian intelligence officers poisoned Sergei and Yulia Skripal in Salisbury using novichok, a deadly Soviet-developed nerve agent. Detectives believe Glushkov may also have been the victim of a professional assassin sent by Moscow, but have so far struggled to identify a suspect or suspects.

Glushkova said she last spoke to her father at 9pm on Sunday 11 March. He was due to appear the next day in the high court to defend himself against a case brought by Aeroflot. “I asked him how he was feeling. He said: ‘I’m prepared. I’m fired up and I’m winning.’ I said: ‘Stay brave. Best of luck. Love you.’”

Glushkova said she called her father at 8pm the next day to see how the hearing had gone. There was no reply. She tried his other devices – and then set off for his house in Clarence Avenue, arriving about 10pm. “I had a key. I opened the door. I knew [immediately] he was dead,” she said.

“I could see some traces of physical harm done to him. The picture was so trashy. It looked like a cheap set up of a suicide. My father was a kind soul, always positive, and a very refined person. I had never seen any sort of depression in him.”

Glushkova said the murder had the hallmarks of a targeted hit. Whoever killed her father entered his terrace house without breaking or damaging the door. Glushkov lived alone with a large ridgeback dog. It appears not to have barked – something Natalia described as “weird”. “The dog was extremely protective of Dad,” she said.

She immediately called for an ambulance and told the operator to alert the police and the British security services. The next few hours were full of grief and horror, she said. Police and paramedics arrived, followed by a special chemical unit response vehicle.

Glushkova said she was tested for exposure to radiation, and had to take off her outer clothes which were bagged up and sent away. Her father was a friend of Alexander Litvinenko, the former FSB officer turned dissident, who was poisoned with polonium in 2006 by two Kremlin assassins.

Glushkova spent hours wrapped in blankets, in the dark and cold, she said, adding: “We were outside the house, both in the street and sitting in a police car.”

Scotland Yard’s counter-terrorism unit has carried out a major investigation into Glushkov’s murder, Operation Bulblet. It has examined hours of CCTV footage and taken nearly 300 witness statements. Detectives believe two Russians poisoned Glushkov in 2013 after meeting him in a Bristol hotel room. He survived.

In August police released footage of a mysterious black Volkswagen van with tinted windows spotted near his home. So far, though, there have been no arrests. “I’m obviously frustrated that there is no movement in my Dad’s case. I would wish the investigation was further on,” Glushkova said.

She urged anyone who was in Clarence Avenue on Sunday 11 March or the early hours of Monday 12 March to come forward – the most probable time when Glushkov, who was 68, was killed. Details of his death await an inquest.

Glushkova was educated in the UK and lives in London. Her mother and brother, Dmitry, are both in Moscow. She believes her father’s case and the attack on Skripal – which the government blames on Moscow and has had greater media attention – could be linked. “Skripal’s case was very loud. If you want something to go unnoticed you make a firework,” she said.

In the 1980s and 1990s Glushkov worked closely with Berezovsky and became Aeroflot’s chief financial officer. He became unpopular with senior figures after clamping down on alleged corruption schemes. In 2000 Berezovsky fell out with Vladimir Putin and fled to London. Soon afterwards Glushkov was arrested in Moscow.

He got out of prison in 2004, moved to the UK, and was granted political asylum. “He managed to become quite happy here in London after a period of adjustment,” Glushkova said. “He loved to travel. He was one of the cleverest men I ever met. He had a PhD. He wrote poems, short stories.”

In exile Glushkov was one of a close-knit group of anti-Putin émigrés, most of whom are now dead. They included Litvinenko, the Georgian billionaire Badri Patarkatsishvili, who died in 2008 of an apparent heart attack, and Berezovsky, who was found dead in 2013.

“There seems to be a pattern here. Every five years. My father died in 2018. He and Badri and Boris were always shown together on Russian TV,” Glushkova said.

In 2011 Glushkov gave evidence in a $5bn (£3.8bn) legal suit brought by Berezovsky against the oligarch Roman Abramovich. Berezovsky lost. He was found hanged in March 2013. Police decided the case was suicide. A coroner recorded an open verdict.

Glushkov was convinced Berezovsky was incapable of killing himself, telling the Guardian in a 2013 interview: “The deaths of too many Russian exiles are happening.” In 2015 he gave evidence to the public inquiry into Litvinenko’s FSB murder, which concluded Putin had “probably” approved the operation.

“A year on I am still grieving,” Glushkova said. “I’m asking for whoever has information about the murder to come forward and inform the police.”