Tax Liability on Investment Bond in Trust

[tommydst]

My father set up a Capital Investment Bond in 1994 with himself and my mother as trustees and my sister and I as joint beneficiaries. The policy included joint life/second death insurance on my father and mother. My father died in 2001 and my mother died in 2009 whereupon the Bond became payable and my sister and I received equal shares. The chargeable gain on the Bond was taxed at 20%. Is there any further tax payable and if so by whom - my mother's estate as she was the trustee, or my sister and I as beneficiaries?

[maths]

What sort of trust is involved?