EGLL DET2Z SID
 

If they say " Climb NOW FL 80 " ...yes

They must either tell you "climb FL80 via SID" or "climb now FL80". If neither of these forms are used, clarify first.

"Climb NOW" is a UK difference from ICAO. Standard ICAO phraseology is "climb unrestricted".

All the differences in phraseology are just a massive threat for international pilots who are often flying in 2 or 3 different parts of the world with different phraseology in the space of a week.

Creates confusion in the cockpit especially if it's one of the pilots first times in the place. Often ends up with one pilot asking the other to ask again to clear things up which seems to bug the controllers, especially at busy airports.

ICAO should really insist that phraseology is standardised. Climb/Descend Unrestricted and Climb/Descend via the SID/STAR is simple and clear.

There is an AIC talking about this, AIC Y023/2010.
http://www.ead.eurocontrol.int/pamsl..._2010_Y_023_en

Hopefully that link works, if not then try the one below and select it in the list.
NATS | AIS - Home

The SID states:

Do not climb above SID Levels until instructed by ATC

and

Due to interaction with other routes do not climb above 6000 until cleared by ATC

So once cleared/instructed by ATC, there are no restrictions unless otherwise stated.

I don’t know if I’m the only one but I do find it frustrating when there is defined standard phraseology and somehow ambiguity is introduced into it. I have been cleared “on”, “with”, “by” and even “using” an arrival and have interpreted that as lateral only when ATC actually meant “via” but couldn’t bring themselves to say it. Clogs up the airwaves with clarification and introduces an element of ??? when there is no need for it. Rant over.

I would say that that is a matter of personal interpretation. When you have pilots from all over the world flying into an area such as London I would think that more than a few would have trouble interpreting the word 'Now' as meaning unrestricted. For me personally that's too generic a word and is far too ambiguous for it to be used in such a congested setting as London airspace. But that's just my opinion.

Exactly my point

I've thought about this as well. I'm still not convinced that if ATC clears you to climb above 6000, the altitude constraints are automatically cancelled. Like the rest of the threads above, there has to be some form of instructions such as "unrestricted" or "climb via SID (to comply altitude constraints)

From post #9, here is the relevant part.

Within UK airspace, for all stages of flight, instructions to climb or descend cancel any previous restrictions, unless the restrictions are reiterated as part of that instruction. Additionally, for aircraft on a SID, the word ‘now’ is added to climb clearances above the SID profile, to highlight that the SID vertical profile is no longer applicable.

eg ‘Jet 123 climb now FL 120’ means that the aircraft should climb directly to FL 120, ignoring the vertical profile of the SID.

Several other posters have also pointed out the UK procedure!

Is this stated in the AIP?

I didn't deal with many outbounds at Heathrow except when on easterlies. My phraseology was always: "Cancel SID, climb FL80".