Holding(s) in Company

TR-1: NOTIFICATION OF MAJOR INTEREST IN SHARES

1. Identity of the issuer or the underlying issuer of existing shares to which voting rights are attached:

GW Pharmaceuticals

2. Reason for the notification (please tick the appropriate box or boxes):

An acquisition or disposal of voting rights

X

An acquisition or disposal of qualifying financial instruments which may result in the acquisition of shares already issued to which voting rights are attached

An acquisition or disposal of instruments with similar economic effect to qualifying financial instruments

An event changing the breakdown of voting rights

Other (please specify):

3. Full name of person(s) subject to the notification obligation:

Prudential plc group of companies

4. Full name of shareholder(s)  (if different from 3.):

See attached schedule

5. Date of the transaction and date on which the threshold is crossed or reached:

22 March 2010

6. Date on which issuer notified:

23 March 2010

7. Threshold(s) that is/are crossed or reached:

See Item 13

8. Notified details:

A: Voting rights attached to shares

Class/type of shares

if possible using the ISIN CODE

Situation previous to the triggering transaction

Resulting situation after the triggering transaction

Number of Shares

Number of Voting Rights

Number of shares

Number of voting rights

% of voting rights x

Direct

Direct xi

Indirect xii

Direct

Indirect

GB0030544687

15,035,088

15,035,088

15,123,621

15,123,621

0

11.66%

B: Qualifying Financial Instruments

Resulting situation after the triggering transaction

Type of financial instrument

Expiration date

Exercise/ Conversion Period

Number of voting rights that may be acquired if the instrument is exercised/ converted.

% of voting rights

C: Financial Instruments with similar economic effect to Qualifying Financial Instruments

Resulting situation after the triggering transaction

Type of financial instrument

Exercise price

Expiration date

Exercise/ Conversion period

Number of voting rights instrument refers to

% of voting rights

Nominal

Delta

Total (A+B+C)

Number of voting rights

Percentage of voting rights

15,123,621

11.66%

9. Chain of controlled undertakings through which the voting rights and/or the financial instruments are effectively held, if applicable: xxi

Prudential plc (parent Company)

M&G Group Limited (wholly owned subsidiary of Prudential plc)

M&G Limited (wholly owned subsidiary of M&G Group Limited)

M&G Investment Management Limited (wholly owned subsidiary of M&G Limited)

M&G Securities Limited (wholly owned subsidiary of M&G Limited)

Proxy Voting:

10. Name of the proxy holder:

N/A

11. Number of voting rights proxy holder will cease to hold:

N/A

12. Date on which proxy holder will cease to hold voting rights:

N/A

13. Additional information:

M&G Securities Limited (wholly owned subsidiary of M&G Limited) has moved to a 10% notifiable interest triggering this notification.

14. Contact name:

Dipesh Varsani / Mark Thomas

M&G Investment Management Limited

15. Contact telephone number:

020 7548 3261 / 020 7548 3266