QUARTER-END POSITION / VERSION 1

WHITE MTNS INS GROUP LTD.

WHITE MTNS INS GROUP LTD

published

Reporting manager: SOUTHEASTERN ASSET MANAGEMENT INC/TN/
Relationship: Associated institution
Record date: 31 Mar 2026
Date meaning: Original Form 13F report period
Quantity: 18,864 shares
Reported value / amount: $41,443,454
Weight and denominator: 2.04% · Calculated: issuer/class value divided by the complete original reported table; not personal wealth
Quarter-end reported price: Not disclosed · Price at record date, not purchase cost
Derived value per reported unit: $2,196.96003 · Reported value ÷ reported quantity (shares); not an observed market price
Source-reported activity: Not disclosed
Coverage: Complete original information table grouped by CUSIP and security class
Reviewed by: DeepSeek AI
Published: 20 Oct 2026

Original regulatory disclosure; 2 original filing line(s) grouped within this issuer/class. Absence from a disclosed table is not private account verification.

Reporting-entity association: Inspect the identity evidence

Original filing attribution · 2 line(s)

Reporting manager: SOUTHEASTERN ASSET MANAGEMENT INC/TN/. 13F HOLDINGS REPORT. These are reported investment-discretion relationships, not proof of beneficial ownership or a personal account. Each original line is counted once, including lines naming multiple managers.

Other included managers: 1 / LONGLEAF PARTNERS FUNDS TRUST · CIK 0000806636; 3 / Greenwood Pine Partners.

ORIGINAL LINE	REPORTED QUANTITY / VALUE	OTHER MANAGER / DISCRETION	VOTING AUTHORITY
82	3,631 shares$7,977,162	No included manager referencedOriginal field: Not stated · Discretion: SOLE	Sole 3,631Shared 0 · None 0
83	15,233 shares$33,466,292	LONGLEAF PARTNERS FUNDS TRUST · CIK 0000806636Original field: 1 · Discretion: DFND	Sole 15,233Shared 0 · None 0

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Editorial note: Independent AI source review 2026-10-21T02:16:00+08:00; batch 74596c44808ba5ff4c67b731e79ffcb3412510c6c3f73314e33c6196e615aae3. Original filing quantities, metadata and row attribution checked. Holdings facts only; corporate-action and period comparisons are not reviewed. This is AI review, not a human or private-account audit.

Sources.

Original disclosure

SOUTHEASTERN ASSET MANAGEMENT INC/TN/ — 13F-HR — 2026-03-31

U.S. SEC EDGAR · Published 15 May 2026 · Collected 20 Oct 2026

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Version history.

Version 1published · 20 Oct 2026

Independent AI source review 2026-10-21T02:16:00+08:00; batch 74596c44808ba5ff4c67b731e79ffcb3412510c6c3f73314e33c6196e615aae3. Original filing quantities, metadata and row attribution checked. Holdings facts only; corporate-action and period comparisons are not reviewed. This is AI review, not a human or private-account audit.

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English factual summary

SOUTHEASTERN ASSET MANAGEMENT INC/TN/ reported 18,864 shares of WHITE MTNS INS GROUP LTD as of 2026-03-31. Reported value: $41,443,454. Weight: 2.04% of Calculated: issuer/class value divided by the complete original reported table; not personal wealth. This is a dated quarter-end position, not a live position, purchase cost or the associated person’s personal account. Filing type: 13F HOLDINGS REPORT. Original rows also reference these included managers: LONGLEAF PARTNERS FUNDS TRUST. Manager references describe reported investment discretion, not beneficial ownership.
Source: U.S. SEC EDGAR — https://www.sec.gov/Archives/edgar/data/807985/000139834426009296/fp0098415-1_13fhr-table.xml | Published: 2026-05-15 | Collected: 2026-10-20T18:02:17.756Z
Record: https://holdingsatlas.com/records/1326df00-77d0-4350-92ed-b89db737b771/

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