Dr Shiela King and Lesley Morrison of Medact, joined Kath MacDonald of CND on the trip.
Dr King said: “The treaty on the prohibition of nuclear weapons came into force in January 2021. The UK is not yet a signatory to the treaty.
"Nuclear weapons are manufactured in the UK and the Nat West Bank, of which RBS is part, lends over £2billion to the industry.
"The organisation Don't Bank on the Bomb organised this protest. We’re asking the bank's customers to support the cause by writing to their bank.”