Holding(s) in Company

TR-1: NOTIFICATION OF MAJOR INTEREST IN SHARES

1. Identity of the issuer or the underlying issuerof existing shares to which voting rights areattached: ii

GW PHARMACEUTICALS PLC

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

An acquisition or disposal of voting rights

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

x

Other (please specify):

3. Full name of person(s) subject to thenotification obligation: iii

FMR LLC

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

See Section 9

5. Date of the transaction and date onwhich the threshold is crossed orreached: v

06 July 2015

6. Date on which issuer notified:

07 July 2015

7. Threshold(s) that is/are crossed orreached: vi, vii

10%

8. Notified details:

A: Voting rights attached to shares viii, ix

Class/type ofshares

if possible usingthe ISIN CODE

Situation previousto the triggeringtransaction

Resulting situation after the triggering transaction

NumberofShares

NumberofVotingRights

Numberof shares

Number of votingrights

% of voting rights x

Indirect

Direct xi

Indirect xii

Direct

Indirect

GB0030544687

25,966,164

25,966,164

25,966,176

25,966,176

10.00%

B: Qualifying Financial Instruments

Resulting situation after the triggering transaction

Type of financialinstrument

Expirationdate xiii

Exercise/Conversion Period xiv

Number of votingrights that may beacquired if theinstrument isexercised/ converted.

% of votingrights

C: Financial Instruments with similar economic effect to Qualifying Financial Instruments xv, xvi

Resulting situation after the triggering transaction

Type of financialinstrument

Exercise price

Expiration date xvii

Exercise/Conversion period xviii

Number of voting rights instrument refers to

% of voting rights xix, xx

Nominal

Delta

Total (A+B+C)

Number of voting rights

Percentage of voting rights

25,966,176

10.00%

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

Proxy Voting:

10. Name of the proxy holder:

FMR LLC

11. Number of voting rights proxy holder will acquire:

12

12. Date on which proxy holder will acquire voting rights:

06 July 2015

13. Additional information:

None

14. Contact name:

Sally-Ann Hatton

15. Contact telephone number:

[email protected], 01737 837148