Question: The Royal Bank of Scotland £20 note is a banknote of the pound sterling, the current cotton note, first issued in which year, bears an image of Lord Ilay, one of the founders of the bank, on the obverse and a vignette on the reverse of Brodick Castle, a castle situated outside the port of Brodick on the Isle of Arran, an island in the Firth of Clyde, Scotland?

Context paragraphs:
Brodick Castle: Brodick Castle is a castle situated outside the port of Brodick on the Isle of Arran, an island in the Firth of Clyde, Scotland.  It was previously a seat of the Dukes of Hamilton, but is now owned by the National Trust for Scotland.

The Royal Bank of Scotland £100 note: The Royal Bank of Scotland £100 note is a banknote of the pound sterling.  It is the largest denomination of banknote issued by The Royal Bank of Scotland.  The current cotton note, first issued in 1987 bears an image of Lord Ilay, one of the founders of the bank, on the obverse and a vignette of Balmoral Castle on the reverse.

Bank of Scotland £50 note: The Bank of Scotland £50 note is a banknote of the pound sterling.  It is the second largest of five banknote denominations issued by the Bank of Scotland.  The current cotton note, first issued in 2007 bears the image of Walter Scott on the obverse and a vignette of the Falkirk Wheel on the reverse.

The Royal Bank of Scotland £50 note: The Royal Bank of Scotland £50 note is a banknote of the pound sterling.  It is the second largest denomination of banknote issued by The Royal Bank of Scotland.  The current cotton note, first issued in 2005 bears an image of Lord Ilay, one of the founders of the bank, on the obverse and a vignette of Inverness Castle on the reverse.

The Royal Bank of Scotland £1 note: The Royal Bank of Scotland £1 note is a banknote of the pound sterling.  It is the smallest denomination of banknote issued by The Royal Bank of Scotland.  The current cotton note, first issued in 1987 bears an image of Lord Ilay, one of the founders of the bank, on the obverse and a vignette of Edinburgh Castle on the reverse.

Bank of Scotland £100 note: The Bank of Scotland £100 note is a banknote of the pound sterling.  It is the largest of five banknote denominations issued by the Bank of Scotland.  The current cotton note, first issued in 2007 bears the image of Walter Scott on the obverse and a vignette of the Kessock Bridge on the reverse.

The Royal Bank of Scotland £20 note: The Royal Bank of Scotland £20 note is a banknote of the pound sterling.  It is the third largest denomination of banknote issued by The Royal Bank of Scotland.  The current cotton note, first issued in 1987 bears an image of Lord Ilay, one of the founders of the bank, on the obverse and a vignette of Brodick Castle on the reverse.

Bank of England £20 note: The Bank of England £20 note is a banknote of the pound sterling.  It is the second highest denomination of banknote issued by the Bank of England.  The current cotton note, first issued in 2007, bears the image of Queen Elizabeth II on the obverse and the image of Scottish economist Adam Smith on the reverse.  Starting in 2020, the current note will be phased out, to be replaced by a polymer note featuring a portrait of artist J. M. W. Turner in place of Smith.

Bank of Scotland £20 note: The Bank of Scotland £20 note is a banknote of the pound sterling.  It is the third largest of five banknote denominations issued by the Bank of Scotland.  The current cotton note, first issued in 2007 bears the image of Walter Scott on the obverse and a vignette of the Forth Bridge on the reverse.

The Royal Bank of Scotland £10 note: The Royal Bank of Scotland £10 note, also known as a tenner, is a banknote of the pound sterling.  It is the third smallest denomination of banknote issued by The Royal Bank of Scotland.  The current cotton note, first issued in 1987 bears an image of Lord Ilay, one of the founders of the bank, on the obverse and a vignette of Glamis Castle on the reverse.  A new polymer note featuring a portrait of scientist Mary Somerville on the front and a pair of otters on the reverse will begin circulating later in 2017.

Supporting paragraphs: The Royal Bank of Scotland £20 note Brodick Castle
Answer: 1987