Does anyone know how to go about claiming stolen inheritance?

My sister lived with my parents and after my Father's death 9 years ago, she cleared the house of all his belongings and claimed she had been given control over all finances etc. At the time I was not concerned, until I realized she had taken everything including all his cameras, lenses, photographs etc. Some lenses are worth £500 each. Since then I had asked her for proof and for my 'share' of the inheritance and she basically laughed it off.
She stayed on as my mother's 'carer', lodging for free, whilst I was doing my mother's laundry, taking her shopping etc and she used to say how she was being bullied by her daughter. My mother claimed physical and verbal abuse. I reported this to social services and in their infinite wisdom tried to move my mother out, which caused her to panic and withdraw her statements she had made to the police and social services.
My mother was in hospital after a fall and whilst I was visiting her, a doctor came to carry out a psych evaluation at my sister's request. I asked whether this was normal for an elderly person (she was 70) after a fall and the doctor advised it wasn't but my sister had requested it in order to obtain the power of attorney.
Christmas 2012, my mother called me in panic stating my sister was emptying the house of all her possessions, I asked her to contact the police and went to visit her a couple of days later. She was sat distressed, unwashed with no money and no food in the house. I took her to my house and asked my partner to help her wash whilst I prepared food. I continued to look after her for the rest of the year until December 2013, when my mother asked me to stop coming round as my sister was back and did not want me around.
Less than a year later she died in hospital. I later learnt she had been committed under the mental health act and after many months of suffering in hospital she died. I was not notified of anything prior nor after and therefore did not attend her funeral. I later learnt, my sister had been living in my mother's house ( warden control housing for elderly people) rent free, bill free and council tax free for over 20 years.
I gave up my job to look after my mother and now I am struggling to find work. I do not claim benefits as I have always worked and paid my way in life. Now my partner and I struggle on a daily basis to make ends meet whilst she is living the high life and travelling the world on money my parents saved.