George Wellwood

I am a Canadian citizen but left Canada in 1985 and have lived in the UK since then. I have an old compnay profit sharing scheme which has had no personal contributions since I left in 1985, and some RSP savings, which were merged together into an RSP some years ago. The value in 1985 was about $12,000 and has grown to $150,000, and I have just cashed it in at the end of this past tax year. There was a 25% Canadian witholding on the full maturity amount. Can I treat all or part of this as a capital gain, or is it all treated as taxable pension income for UK tax purposes?