Big Yellow Regulatory News (BYG)

1.

KEY INFORMATION

(a)

Full name of discloser:

Massachusetts Financial Services Company

(b)

Owner or controller of interests and short positions disclosed, if different from 1(a):

The naming of nominee or vehicle companies is insufficient. For a trust, the trustee(s), settlor and beneficiaries must be named.

(c)

Name of offeror/offeree in relation to whose relevant securities this form relates:

Use a separate form for each offeror/offeree

BIG YELLOW GROUP PLC

(d)

If an exempt fund manager connected with an offeror/offeree, state this and specify identity of offeror/offeree:

(e)

Date position held/dealing undertaken:

For an opening position disclosure, state the latest practicable date prior to the disclosure

04 December 2025

(f)

In addition to the company in 1(c) above, is the discloser making disclosures in respect of any other party to the offer?

If it is a cash offer or possible cash offer, state “N/A”

NO

2.

POSITIONS OF THE PERSON MAKING THE DISCLOSURE

If there are positions or rights to subscribe to disclose in more than one class of relevant securities of the offeror or offeree named in 1(c), copy table 2(a) or (b) (as appropriate) for each additional class of relevant security.

(a)

Interests and short positions in the relevant securities of the offeror or offeree to which the disclosure relates following the dealing (if any)

Class of relevant security:

10p ordinary (GB0002869419)

Interests

Short Positions

Number

%

Number

%

(1)

Relevant securities owned and/or controlled:

4,289,833

2.18 %

(2)

Cash-settled derivatives:

(3)

Stock-settled derivatives (including options) and agreements to purchase/sell:

Total

4,289,833 *

2.18 %

* Massachusetts Financial Services Company and/or its affiliates do not have discretion regarding voting decisions in respect of 386,238 shares that are included in the total above.

All interests and all short positions should be disclosed.

Details of any open stock-settled derivative positions (including traded options), or agreements to purchase or sell relevant securities, should be given on a Supplemental Form 8 (Open Positions).

(b)

Rights to subscribe for new securities (including directors’ and other employee options)

Class of relevant security in relation to which subscription right exists:

Details, including nature of the rights concerned and relevant percentages:

3.

DEALINGS (IF ANY) BY THE PERSON MAKING THE DISCLOSURE

Where there have been dealings in more than one class of relevant securities of the offeror or offeree named in 1(c), copy table 3(a), (b), (c) or (d) (as appropriate) for each additional class of relevant security dealt in.

The currency of all prices and other monetary amounts should be stated.

(a)

Purchases and sales

Class of relevant security

Purchase/sale

Number of securities

Price per unit

10p ordinary (GB0002869419)

Purchase

217

10.7400 GBP

(b)

Cash-settled derivative transactions

Class of relevant security

Product description e.g. CFD

Nature of dealing e.g. opening/closing a long/short position, increasing/reducing a long/short position

Number of reference securities

Price per unit

(c)

Stock-settled derivative transactions (including options)

(i)

Writing, selling, purchasing or varying

Class of relevant security

Product description e.g. call option

Writing, purchasing, selling, varying etc.

Number of securities to which option relates

Exercise price per unit

Type e.g. American, European etc.

Expiry date

Option money paid/ received per unit

(ii)

Exercise

Class of relevant security

Product description e.g. call option

Exercising/ exercised against

Number of securities

Exercise price per unit

(d)

Other dealings (including subscribing for new securities)

Class of relevant security

Nature of dealing e.g. subscription, conversion

Details

Price per unit (if applicable)

4.

OTHER INFORMATION

(a)

Indemnity and other dealing arrangements

Details of any indemnity or option arrangement, or any agreement or understanding, formal or informal, relating to relevant securities which may be an inducement to deal or refrain from dealing entered into by the person making the disclosure and any party to the offer or any person acting in concert with a party to the offer:

Irrevocable commitments and letters of intent should not be included. If there are no such agreements, arrangements or understandings, state “none”

None

(b)

Agreements, arrangements or understandings relating to options or derivatives

Details of any agreement, arrangement or understanding, formal or informal, between the person making the disclosure and any other person relating to:

(i) the voting rights of any relevant securities under any option; or

(ii) the voting rights or future acquisition or disposal of any relevant securities to which any derivative is referenced:

If there are no such agreements, arrangements or understandings, state “none”

None

(c)

Attachments

Is a Supplemental Form 8 (Open Positions) attached?

NO

Date of disclosure

05 December 2025

Contact name

Nikki Cagan

Telephone number

+442074297243