---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-25-308800"
form_type: "8-K"
ticker: "WRB"
cik: "0000011544"
company_name: "BERKLEY W R CORP"
filed_at: "2025-12-05T23:59:59+00:00"
generated_at: "2026-05-16T14:12:16.813846+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.6
calibrated_materiality_score: 0.6
confidence: "high"
source: SEC EDGAR
---

# Mitsui Sumitomo Insurance acquires beneficial ownership of at least 12.5% of WRB

## Summary
- MSI now holds ≥12.5% of WRB outstanding common stock under previously announced Berkley family agreements.
- MSI shares will be voted per Berkley family recommendations except for proportional voting in limited cases.
- No shares were purchased from the Berkley family or the Company itself.
- MSI expects to complete its full investment under the agreements in Q1 2026.
- The agreements were originally filed with the SEC on March 28, 2025.

## SEC filing metadata
- accession: 0001193125-25-308800
- form_type: 8-K
- ticker: WRB
- cik: 0000011544
- company_name: BERKLEY W R CORP
- filed_at: 2025-12-05T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.6
- calibrated_materiality_score: 0.6
- confidence: high
- sec_items: 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/11544/000119312525308800/0001193125-25-308800-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/11544/000119312525308800/d53561d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-25-308800
- JSON: https://secwatch.observer/filing/0001193125-25-308800.json
- Plain text: https://secwatch.observer/filing/0001193125-25-308800.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.