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Sigrid Verbert Sigrid Verbert Advisory · Est. 2011

Currently accepting principals for Q1 2026

How the practice works.

The work is structured. The pace is deliberate. The relationship, once entered, tends to last.

§ I — Mechanics

The three phases of an engagement.

Every principal passes through the same three phases, in the same order. There are no shortcuts between them and no alternative paths around them. The structure exists because each phase produces a different kind of deliverable, and because the diagnostic must be allowed to fail honestly — it is the only honest place to begin.

I.

The diagnostic.

Ninety minutes, in person or by encrypted video, conducted in whichever of English, French, German, or Dutch the principal prefers. The diagnostic is paid (€4,500, invoiced in advance) and produces no strategy, no deck, and no recommendations. It produces a single written record — the decision memo, drafted within ten working days — that records what was discussed, what was held back, and what the principal appears to be deciding without yet knowing it.

The diagnostic may conclude that the practice is not the right fit. It does, in roughly one in five cases.

II.

The decision memo.

The memo is the artefact the principal keeps. It is a typed, signed document of between six and twelve pages that names the inflection the principal is facing, the options visible from where they sit, the questions they have not yet been asked by anyone in their existing circle, and a recommendation — provisional, but defensible — on whether a retainer is warranted.

It is the only document Sigrid signs in her own name. It is not shared with any third party under any circumstance.

III.

The retainer.

A retainer is a standing, indefinite engagement, terminable by either party on thirty days' notice, with a minimum commitment of six months. Sessions are scheduled at a cadence set jointly — typically monthly, occasionally fortnightly during an active transaction. Between sessions, principals have direct written access to Sigrid, with a response commitment of one working day.

The retainer fee is set individually, calibrated to the complexity of the principal's situation, and reviewed annually. It is not published and is not negotiable downward.

§ II — Sequence

A second reading, for those who skim.

The same three phases, set vertically as a sequence. Read either section; the argument is the same.

  1. I

    Phase one

    Diagnostic conversation

    90 minutes · paid in advance · written follow-up within 10 working days

    A single, confidential session. No preparation is asked of the principal beyond showing up with the question they have not yet been able to put into words.

  2. II

    Phase two

    Decision memo

    6–12 pages · signed · delivered once, to the principal alone

    The diagnostic, written down. The principal may accept, decline, or defer a retainer on the basis of the memo alone.

  3. III

    Phase three

    Retainer

    6-month minimum · monthly sessions · direct written access

    A standing relationship. The work happens between sessions as often as during them.

§ III — Operating record

Evidence of a working method, not a marketing pitch.

Numbers that are verified, narrow, and deliberately small. They are stated here because principals ask about them, and because the practice is built around them.

38

Concurrent principal cap

Enforced since 2014. The practice has never carried more than thirty-eight.

5.7yrs

Average client tenure

Twenty-two current clients are in their seventh year or beyond.

81%

Diagnostic-to-retainer conversion

Across all diagnostics conducted since 2011. The remainder conclude that the practice is not the right fit.

100%

Last-four-cohort renewal rate

Every principal who entered a retainer in the last four cohorts remains a principal today.

A small private reading room in a Brussels townhouse, used for diagnostic conversations.
Reading room, Avenue Louise, Brussels. Where diagnostics are conducted in person.

The cap is not a marketing device. It is the condition under which the work remains worth doing — for the principal, and for the practitioner who has to live inside the consequences of what she advises.

— Sigrid Verbert, internal practice note, 2014

§ IV — Entry point

Request a diagnostic conversation.

Ninety minutes. One written memo within ten working days. €4,500, invoiced on confirmation. No preparation is required of you; the question you arrive with is sufficient.

If the diagnostic concludes that a retainer is not warranted, the memo will say so plainly, and the engagement ends there.

Request a Diagnostic Conversation Read the principal's biography

Office hours: Monday–Thursday, 09:00–17:00 CET. All enquiries answered within two working days. Office: Avenue Louise 480, 1050 Brussels.