EXHIBIT 99.1

Shire Pharmaceuticals Group plc
Hampshire International Business Park,
Chineham, Basingstoke RG24 8EP UK
Tel +44 1256 894000 Fax +44 1256 894708
http://www.shire.com

19 March 2004

Shire Pharmaceuticals Group plc (the “Company”)

The Company announces that it was notified on 15 March 2004 under Sections 198 to 202 of the Companies Act that Aviva plc, through its subsidiary Morley Fund Management Limited, held solely for investment purposes in aggregate 14,793,326 ordinary shares of £0.05p each in the capital of the Company. These holdings represent 3.09 per cent of the issued ordinary share capital of the Company.

T May
Company Secretary

For further information please contact:

Investor Relations

Cléa Rosenfeld +44 1256 894 160

Notes to editors

Shire Pharmaceuticals Group plc

Shire Pharmaceuticals Group plc (Shire) is a global specialty pharmaceutical company with a strategic focus on meeting the needs of the specialist physician and currently has a range of projects and products in the areas of central nervous system (CNS), gastrointestinal (GI), and renal diseases. Shire has operations in the world’s key pharmaceutical markets (US, Canada, UK, France, Italy, Spain and Germany) as well as a specialist drug delivery unit in the US.

For further information on Shire, please visit the Company’s website: www.shire.com